Cited by M. Greenwood, 'On Digestion in Hydra, with some Observations on the Structure of the Endoderm', Journal of Physiology 9 (5-6) (1888), pp. 317-344.
Description:

'In the Archiv für Mikros. Anat. XXIX, Nussbaum published a paper on the "Divisibility of Living Substance." In this paper, after reviewing the specific characters of Hydra as described in the writings of earlier workers, he distinguished among such specimens as are destitute of chlorophyll, Hydra fusca, Hydra grisea, and the straw-coloured Hydra (H. attenuata, Roesel). Such characters as colour, the number of tentacles present, sharp or gradual passage of the Hydra's body into its narrower, paler foot formed the basis of classification.

When I began to make the observations which have led me to write this paper Nussbaum's account had not appeared, and I did not record the differences which existed before death in the specimens of Hydra which I examined. Since this is the case and since, further, I have been unable in later investigation to associate any certain variation in structure with variation in number of tentacles and in depth of tint, I apply the name Hydra fusca alike to forms which are bright brown or very dark brown, which have six, seven or eight tentacles and which taper gradually to their basal point of attachment the sucker-or exhibit a cylindrical body and a well-miarked narrower columnar foot. I do this with the greater confidence since Nussbaum [note: 'M. Nussbaum. Archiv f. Mik. Anat. XXIX. 1887.'] after describing the characters of the endoderm of Hydra grisea adds that in the case of Hydra fusca the structure is on the whole the same.' (317)

 

'In the living membrane of the body cavity of any brown specimen of Hydra it is generally comparatively easy to distinguish two sorts of cells - the larger vacuolate endoderm cells with amoeboid ends andretractile cilia, and, lying singly between groups of these, smaller cells destitute at all times of the vacuoles which form so conspicuous a feature of the endoderm generally, and (as far as I have seen) without amoeboid movement. Many descriptions of the larg,er vacuolate cells are given by various observers, since the time of Leydig (1854); it is only Nussbaum [note: 'M. Nussbaum. Op. cit.'] and Jickeli [note: 'C.F. Jickeli. Morpholog. Jahrbuch. Bd. VIII. 1883.'] I believe who have described and figured cells of two kinds. To the smaller elements of the endoderm both observers give the name of gland cells; but while Nussbaum describes their appearance as varying in different specimens anid therefore hints at the performance of correlated function, he brings forward no experimental evidence of their glandular nature, and such evidenice is wanting in Jickeli's accounit. I may say at once that I shall have to record observations which seem to support the view that, during digestion especially, active secretory processes go on in these cells. And therefore, although these observations must be weighed against others not clearly in harmony with such an hypothesis, or not best explained by it, I keep the phrase used by Nussbaum and Jickeli and speak as they do, of gland cells.' (317-318)

 

'It is in this apical mass that the slight power of amoeboid movement possessed by the cells becomes manifest, and in specimens examined in the fresh state it is exhibited by the formation of blunt hyaline projections which arise fromn the apex of each cell and are never probably more than one-fourth of the depth of the aggregation of substance from which they spring. Retractile cilia may also be given off from the endoderm into the body cavity, one or two taking origin in each cell. I do not believe that they co-exist with the blunt amoeboid protuberances, and I have not seen them in living, teased specimens: it may be then that the power of emitting a long cilium is lost with the integrity of the animal, the injury effected by rupture allowing only the formation of a lobate projection. (I ought to add that Nussbaum [note: 'M. Nussbaum. Op. cit.'] describes the occurrence of ciliary action for some ten minutes after teasing a fresh Hydra, and says that later only blunt pseudopodia are formed.) That part of the protoplasm of the endoderm cell which is not immediately concerned in the putting out of a projection is, in the fresh state, very faintly granuilar, while the region which moves is hyaline; this differentiation is not however made permanent by hardening reagents, and I am unable to make any very definite statement of the nature of the structural details brought out by their action.' (319)

 

'When a living Hydra is teased under the microscope, little masses of cohering pigment grains are sometimes seen to be turned out of the yet moving endoderm cells, much as carmine or starch is under certain circumstances passed from the substance of the Amoeba. This may of course be a phenomenon of lesion (for the injury inflicted by tearing must be severe), and may correspond to no normal discharge of pigment from the body; but certain statements of other investigators and of my own observations incline me to the view that the ejection represents, though perhaps in an abnormally explosive manner, a normal excretion of matter... 

... I have noticed that in the endoderm cells of a well-fed Hydra the pigment is generally difficult to distinguish, though sometimes it is to be found not now as normally at the apex of the cell, but moved down one side wall. In the endoderm of a fasting animal it is most conspicuous, partly because here the cells are comparatively empty and but few nutritive spheres strike the eye, but also I think because it is actually great in quantity (cf. figs. 3 and 4, PI. VI.). I do not forget that Nussbaum [note: 'M. Nussbaum. Loc. cit.'] describes the tint of Hydra fusca as paling in long hunger, and that this at first sight appears contradictory of the statement just made. The contradiction is, I think, only apparent, for it must be remembered that long hunger means the disappearance of many opaque bodies,-the proteid spheres, and that possibly the highly vacuolate, partially empty cells are more transparent than are those loaded with reserve material. And the assertion that pigment is absolutely abundant in the fasting condition is not incompatible with the belief that at this time a slow discharge of it is going on, indeed the results of such discharge were, I imagine, seen in an experiment quoted above.' (329-330)

 

'I have said that fragments of proteid reacting like the nutritive spheres may lie at the apex of an endoderm cell during hunger in marked fluid surroundings, and fig. 9, Pl. VI. represents an instance of the considerable vacuole in which pigmented proteid is at times found. Nussbaum [note: 'M. Nussbaum. Op. cit.'] too describes balls, crystals and granules of a yellow or brown colour as held in bladder-like formations in the apices of the endoderm cells' (331-332)

 

'And with this brief account of it [the structure of the endoderm] I bring to a close my description of the large vacuolate cells, and turn to consider the other elements of the endoderm, the "Drüsenzellen" of Nussbaum [note: 'M. Nussbaum. Op. cit.'], and Jickeli [note: 'C.F. Jickeli. Op. cit.'].

The gland cells. These, according to Nussbaum, are ciliated. I have found that they generally appear with rounded apices (quiite conceivably because in preparation their cilia have been retracted), and in living specimens do not readily show amoeboid movement; basally they taper to a long process, which passes to the supporting lamella, and gives them the pyriform shape noticed by Jickeli. Each cell has a nucleus not differing from those of the endoderm generally, and each has cell substance which forms here no sheath-like investment for a central collection of fluid, but is a solid mass in which certain temporary constituents of the cell at times lie embedded. These are solid spherical bodies, smaller than the typical nutritive spheres of the absorbing endoderm cells, but resembling them markedly under the action of staining reagents, or indeed of chemical reagents generally. Thus persistence under treatment with osmic acid, with assumption of a yellow brown colour, and loss of individuality in solutions of acids and alkalis characterize these spherules; they are swollen by dilute potash and in stronger solutions burst or become invisible; in 10 per cent. solutions of sodium chloride they dissolve. It is clear however that, if the name which I have adopted for the containing cells from the writings of earlier workers be truly indicative of their function there must be, underlying this apparent similarity, essential differences between the spherules and the proteid spheres which are formed when nourishment is abundant. And observation of the mode of origin and the fate of the smaller bodies makes it plain that such differences do exist. For it becomes clear not only that the spherules come and go, but that under suitable conditions specimens may be obtained which indicate the manner of their disappearance, and further that their occurrence is definitely related to the manifestation of digestive activity.' (332-333)