Cited by M. Greenwood, 'On the Digestive Process in some Rhizopods. Part II.', Journal of Physiology 8 (5) (1887), pp. 263-310.
Description:

Explanation of plate:

 

Fig. 1. Amoeba Proteus.

The outlines are drawn under B. Oc. 3 (Zeiss), the details of internal structure are filled in from observation with Obj. D. Oc. 3.

n = nucleus. A. B = Infusoria undergoing digestion in vacuoles of secreted fluid. (a) (β) = similar Algae, one more recently ingested than the other (brown). In both the fluid which is digesting them lies between the cell wall and shrunken protoplasm. K. Crystalline ingestion.

C. V. = contractile vacuole.

 

Fig. 2. Hind end of Amoeba Proteus. Zeiss. Oc. 3, Obj. D.

Pseudopodia are meeting round a Stylonychia St. which lies in the vacuole of ingestion. f = point of fusion of meeting ectosarc.

 

Fig. 3. Amoieba Proteus; 2 lateral pseudopodia.

Outline as observed with Oc. 3, Obj. D.

Details filled in under Oc. 3, Obj. F.

a, β = Two Infusoria with adherent carmine lying in digestive vacuoles.

A = Three Monads forming one ingestion.

Chl = Chlorococcus after 2 days' enclosure.

 

Fig. 4. Hind end Amoeba Proteus to show act of ejection and preparatory arrangements.

e = Euglena after 3 days' enclosure.
i = Infusorian.
r = momentary break, after escape of Euglena.

 

Fig. 5. Amoeba Proteus. Hind end.

a, b, c, watched under Oc. 3, Obj. D.

d, e, f, g,   "             "        "          " F.

To show ingestion of, and subsequent change in the vesicular expansion of the Amopeba's ectosarc, this expansion being probably, before its ingestion, constricted off from the main part of the animal.

In all the diagrams.

I = a group of Monads contained by the vesicular expansion.

C = a small mass of carmine enclosed in a like manner.

R = a granular accumulation ? endosarc, or ? a half-digested Monad which was discernible throughout the first changes seen.

In a the ectosare expansion is almost free.

In b it seems merely adherent, and the extreme hind end of the Amoeba is taking on a shallow funnel shape.

In c this funnel advances over the (probably) freed sphere.

In d the ingestion is complete, the sphere lies deeply, but approaches the upper surface of the Amoeba in e.

In f fluid is lost from within the sphere and secreted round it; its walls have collapsed; the carmine and Monads are still distinguishable.

In g digestive change has become more extended.

 

Fig. 6. Hind end Amoeba Proteus.

Observed under Oc. 3, Obj. F.

A, B = Infusorial ingestions, B holding carmine.

C = carmine ejection on stimulus of transference to fresh water.

D = Desmid, very old ingestion.

 

Fig. 7. Hind end Amoeba Proteus.

Observed under Oc. 3, Obj. F.

To show loss of Closterium without vactuole (Cl) and slowly retreating sheet of investing ectosarc (ec).

 

Fig. 8. Actinosphaerium Eichornii.

Outlines of animal and of digestive vacuoles traced with Oc. 3. Obj. B.

Details of protoplasmic bars filled in under Obj. D, Oc. 3.

To show simultaneous existence of many digestive vacuoles and changes in ingested Euglenae.

A = recent ingestion. B Later. C and D near ejection stage.' (285-286)

 

Fig. 1 in text:

'Scytomonas [note: 'cp. Saville Kent, Manual of Infusoria, I.'] differs from Monas in the greater rigidity of its external layer. The increase in rigidity is apparently associated with increased indigestibility, and Scytomonas, though after enclosure it becomes surrounded by a well-marked vacuole, is never at any time represented by a mass of granules. Rather it becomes reduced to a pale sphere, all trace of flagella and internal structure being lost. Such it is when the solvent fluid has passed from its immediate neighbourhood, and as such it may be ejected from the Amoeba (Pl. VIII. Fig. 1 B). Here it wouild appear is the beginning of an insoluble residue, a residue which becomes well marked in inaestions to be considered hereafter, which may take the form of differentiated investments and appendages of the prey on the one hand, and on the other of structural complexity or accidental heterogeneity of its contents.' (266-267)

 

Figs. 1, 3 and 6 in text:

'in any adult Alga, at least of the Chlorophyceae, we may distinguish cell-wall, protoplasm, and chlorophyll held in the protoplasm. In the forms which most frequently fall a prey to Amoeba the chlorophyll is generally diffused; occasionally however it may be present in chlorophyll corpuscles which form specialised parts of the otherwise colourless protoplasm. Of these elements the protoplasm undergoes the most marked change; for, at first adherent to the cell-wall, it presently becomes an irregular mass separated on all sides from the cell-wall by fluid. (Fig. 1, α.) The formation of this irregular mass is probably truly indicative of loss of substance and not of such a change as occurs in plasmolysis since the Algae examined, viz. Chlorococcus, Protococcus, Desmids, Diatoms are not those which are possessed of the most conspicuous cell-vacuoles.

When chlorophyll is present in ingesta in the form of corpuscles, the outlines of these may still be seen while the less modified protoplasm between them is shrunken and changed; when however the chlorophyll is generally diffused, it follows and emphasizes the
change of form in the cell substance which holds it. 

And such chlorophyll is not itself unaltered. An Amoeba which has previously been in the neighbourhood of small Algae often exhibits upon examination ingesta in which the colour is dark brown, and indeed it may be that the presence of organisms alike save for their difference of tint indicates that occurrence of digestive change which continued watching, reveals. (Figr. 1, β.) It must not be thought however that the chlorophyll and protoplasm exhibit parallel series of changes; the action exerted by the Amoeba on both is slow when compared with the rapid digestion of Monas, of Eualena, of Glaucoma, but the slowness is especially marked in the case of the colouring-matter.

Thus, shrinking first sets in (and this is only apparent in two to three days), and three, five, six days may pass and leave the chlorophyll still green. (Cf. Fig. 3, Chl.) Although this change is so slow I think it is completed before ejection of the Algae unless they are lost as a result of lesion; and indeed a Desmid, a Diatom, or a spore may be traced in the substance of the Amoeba for two or three days after digestive action is, as judged by the eye, complete. (Fig. 6, D.)' (270-271)

 

Fig. 2 in text:

'The act of ingestion and subsequent position of the ingested body. I have previously described the act of ingestion of solid particles and have said that the ectosarc is drawn like the rim of a funnel ovel the prey it is about to enclose. I may poilnt out now that this advance of the ectosarc takes place in two stages; there is a lateral meeting of encircling pseudopodia (Pl. VIII. Fig. 2f), and fusion of their external boundaries before the enclosing films pass above and below the prey. The ingestion of any small object is almost always effected at the hind end of the Amoeba, but a relatively large organism (Stentor, Stylonychia, or a Rotifer) may induce a marked and general change in the form of its captor.' (265)

 

Figs. 3 and 6 in text:

'The secretion which fills a digestive vacuole then, holds somle substance which is active on proteid matter; further, it is probable that the activity goes on in a neutral medium. It has been mentioned above that carmine when taken in alone speedily lies in contact with the Amoeba's substance. But it may be enclosed, possibly by accident, in a vacuole of ingestion which holds a Protococcus or a Scytomonas, and Infusoria which have in the first place taken in carmine may be ingested and changed. (Fig. 6, B. Fig. 3, α. β.) In neither case do the carmine grains undergo solution; their colour is undiffused, their outline still sharp after two to three days. Now sodium carbonate .1% brings about under the microscope quite obvious solution of carmine; the absence of any change in digestion may therefore with some amount of certainty be taken as the expression of the absence of an alkali in the digestive fluid.' (272)

 

Figs. 4 and 6 in text:

'The conditions which accompany ejection. In speaking of this point, which forms the natural conclusion to that just briefly considered, it may be well to deal at the same time with nutritious and innutritious ingesta. And I have to acknowledge ignorance of the conditions which in Amoeba are necessary for the formation of an excretory vacuole. Fluid, though so often present round the débris of digested food cannot be necessary for the act of expulsion since crystals, litmus, carmine, and starch may be passed to the exterior without such accompaniment. Indeed an Alga is sometimes ejected with no marked surrounding fluid, and when as often happens, on mounting an Amoeba a large vegetable ingestion is prematurely expelled, its exit is quite gradual, and while part lies freely in the surrounding water another part is yet invested by a sheet of hyaline ectosarc which is gradually withdrawn [note: 'Leidy illustrates a like gradual passage from the endosarc in the case of an Alga. Op. cit., Plate VIII. Fig. 29.']. Here the expelling ectosarc leaves the endosarc behind, but it may happen that granules and crystals flow right up to the end from which innutritious matter is being passed. (Fig. 6.) Even in this case the rupture effected by transit of the solid matter is so soon repaired that there is no escape of endosarc; indeed (if it be justifiable to use the term rupture at all) I have only once seen any indication of solution of continuity, and that was momentary and occurred in the ejection of a Euglena which was probably surrounded before its exit by a small quantity of fluid. (Figs. 4. e. r.)' (276-277)

 

Figs. 4, 6 and 7 in text:

'It has been suggested above that it is mechanical inconvenience to the Amoeba which limits the stay of ingesta, rather than their nutritious on non-nutritious natuire. It is probable however that indigestible matter is often rejected when more nutritious ingesta are available. Thus while starch may be enclosed for seven days, it may be lost after four or five days upon the ingestion of Monads, or even before that time if its grains are large relatively to the size of the Amoeba. In like manner Euglena may replace Chlorococcus and Desmids may be expelled when Infusoria are taken in. The region in which ejection occurs is much more determinate than is the mechanism by which it is effected, and I believe that all ingesta are passed out from the hind end. (Cp. Figs. 4. 6. 7.) They take up a position there it may be some hours before they leave the substance of the Amoeba, and generally keep this position until the end; an excretory vacuole when this is present may be formed before or after the final passage backwards, but typically it becomes evident only a short while before the actual ejection.' (277)

 

Fig. 5 in text:

'Self-digestion. Before passing to the consideration of Algae, ingesta in which the structural, insoluble element is very marked I must describe a series of events seen in Amoeba Proteus and diagrammatically represented in Pl. VIII. Fig. 5. Seen only once, this series may form an insecure basis for generalisation: it is nevertheless too curiouis to leave unrecorded. 

The Amoeba in question had been under observation for six days. When examined on the seventh morning it held many ingestions, in vacuoles - Infusoria with adherent carmine grains, and an Alga which, during an enclosure of two days had remained bright green. At 12.45 the hind end of the Amoeba had the appearance indicated by Fig. 5 a. A vesicle bounded by substance, hyaline save at the point K, projected from the animal's body. In the fluid which filled this projection lay five extremely small Monads and one readily distinguishable carmine grain; the Monads were in active movement. The continuity which apparently existed at this stage between the proximal part of the vesicle and the protoplasm of the Amoeba became less evident in a few minutes, and at the stage sketched in Fig. 5 b, I thought there was adherence but no structural connection. But at this point the Amoeba's hind end took on the form of a shallow funnel, rims of ectosarc advanced round and over the vesicle or portion of substance which I believe had just been cut off (Fig. 5 c) and by 1.30 P.M. complete enclosure was effected (Fig. 5 d). The vesicle lay then within the substance of the Amoeba but towards the lower surface so that it was necessarily viewed through the clear, superficial ectosarc and granular more internal protoplasm. Through this however might still be distinguished the rim of clear matter with a slight accumulation at one point, while the carmine lying within was also evident, and four of the Monads could be seen.

At 2.35 P.M. (Fig. 5, e) the ingestion showed a definite external boundary but the fluid it held when enclosed was reduced in amount, and the wall of the vesicle was expanded inwards and showed a jagged internal edge.

At 2.50 P.M. (Fig. a, f) the vesicle was represented by a collapsed sac lying in a well-marked vacuole; within it the Monads could be dimly distinguiished and the carmine showed plainly.

Digestive change now progressed; at 3.50 P.M. the mass was still irregular while all trace of the Monads had gone; and at 4.30 P.M. it had become rounded and was indistinguishable except by memory from an Infuisorian holding carmine.

At 6 P.M. the rounded mass with its vacuole had left the bind end of the Amoeba and passed into the more actively moving anterior region, while the next morning a very small vacuole still surrounded it and the solution was far from complete

It will be seen that I have not recorded the protrusion of this eventually digested vesicle from the substance of the Amoeba, and that I did not watch the entrance of the Monads into the fluid which it contained.' (269-270)

 

Fig. 6 in text:

'The ingestion of innutritious substances. When insoluble matter is taken in a comparatively massive form (as when starch grains, litmus, crystals and single lumps of carmine constitute the ingesta) it speedily lies in contact with the endosarc of the Amoeba, and after a stay of varying length is rejected. (Fig. 6, C.) Carmine may, however, be administered in a state of very minute division, and Indian ink when rubbed with water is almost invariably finely particulate. And fragments of carmine or of Indian ink of such small size very commonly move after their ingestion, not freely, but gathered into grotups by a basis of hyaline substance which is generally spherical and often difficult to observe. I thought at first that this was a phenomenon bearing much resemblance to the "binding" of carmine into balls which Ehrenberg describes in ingesting Infusoria. But as has been said Indian ink too may possess this basis; and since Indian ink frequently, and carmine, when sufficiently finely divided, cling to the hind end of the Amoeba before ingestion, while it is at the hind end, as is well known, that ingestion does take place, it seemed to me just possible that a finely particulate ingestion (and no nutritious matter which I have seen reaches a state of such minute division) might be accompanied by an infolding of the ectosarc. This infolding is by subsequent constriction separated off, and moves, with the grains which cling to it, through the substance of the enclosing animal. Since the grains so provided with a "basis" are during their enclosure no more changed than are the larger masses which lie free in the endosarc this connection cannot have digestive significance, and its occurrence seems very improbable in face of the account of change of ectosarc vesicle which I have recorded above. I notice the phenomenon here because it characterized about 90 % of the Amoebae in which ingestion of carmine was observed.' (275)

 

Fig. 8 in text:

'It has been said before that great change in the colouring matter chlorophyll is no necessary part of digestion in Actinosphaerium. When Euglenae are ingested they do not take on the dark brown tint, characteristic of them after twenty-four hours' stay in the Amoeba. They are markedly changed, and so much so that the chlorophyll which at first coloured their substance presently gives a yellow-green colour to the vacuole in which they lie (Pl. VIII. fig. 8 D). The crystalline bodies are unaffected; the chlorophyll never spreads into the surrounding protoplasm of the Actinosphaerium nor invades neighbouring structural vacuoles, and becoming more yellow, but as I think rarely dark brown, it is ejected after a stay possibly some hours longer than that made by an ingested Infusorian.' (231)

 

Fig. 9 in text:

'The act of ingestion. This is sometimes effected without any noteworthy aid from the filiform pseudopodia: these may, it is true, grasp a quiescent prey or cling to an object that is moving, but in the specimens of Actinosphaerium in which I saw most active ingestion, contact of an Infusorian or of Euglena with the main body of its captor was the only antecedent which I could immediately connect with the enclosure that followed. There is a possibility of this enclosure at any point in the circumference of Actinosphaerium; at any point thierefore an ingestive pit may be formed, and films of the surrounding substance may be drawn over the prey. The advance of these films is usually so slow that the steps of it cannot be followed; it may happen however (Pl. IX. fig. 9 B), that when a very active Infusorian is being taken in, a tongue-like protrusion of hyaline substance is seen to run out under it, starting from the middle of the unifornmly present depression.' (279)

 

Figs. 9 and 10 in text:

'We have to deal then chiefly with bodies that are changed after ingestion, and among them may be distinguished small and larger colourless Infusoria, Rotifers, and small Crustaceans: Euglena is taken up greedily and enclosed Algae may also be found.

Up to a certain point these organisms have a common fate; they are all surrounded by vacuoles, changed while thus surrounded, and ejected from fluid when the digestive act is at an end. (PI. IX. figs. 9 and 10.) As ingestion may take place at any point of the external boundary of the body substance, and as in great activity one ingestion follows another rapidly, it comes to pass that somnetimes many digestive vacuoles, with contents in various stages of change, lie scattered through the body of the Actinosphaerium. And while any vacuole is at first peripheral it may lie more deeply as digestion proceeds, though there is, before loss of food-remains occurs, a final passage towards the superficial layer of the enclosing protoplasm.' (279)

 

Fig. 10 in text:

'it should be noticed that the fluid of the vacuole as a rtule increases in amount during digestion, and is never so relatively abundant as before the act of ejection. (Pl. IX. fig. 10.)' (280)

'In Actinosphaeriurm it is quite rare to find on any morning traces of organisms which had been ingested on the previous day; and while the "cuticular hooks" of Stylonychia do form a residue which is indigestible, that is, is ejected unchanged, there is quite considerable breaking down of Infusoria in which cuticle and "myophan" layer are well developed. Such Infusoria are generally represented aftex six to eight hours by a colourless granular mass in a large thin walled vacuole (Pl. IX. fig. 10); this mass is speedily discharged and carries with it any accidental food contents of the organism which it represents.' (230-231)