250 PROFESSOR E. RAY LANKESTER. 



rophyllaceous), previously colourless, lying in the cell- 

 protoplasm, gave a blue colour with iodine. I would venture 

 the surmise that in H//dra viridis, as in Spongilla, the pro- 

 duct of assimilation due to the activity of the chlorophyll- 

 corpuscles is very rapidly diffused, and does not take the 

 form of starch as in green plants, or if it does take that form, 

 it is after diffusion from the seat of assimilation. 



A very strong argument against Brandt's theory of the 

 parasitic nature of the chlorophyll-corpuscles is found in the 

 fact noticed by Kleinenberg, that minute angular fragments 

 of a green colour are often present, together with the normal 

 corpuscles (PL XX, fig. 21). In fact, in Hydra, as in 

 Spongilla, though there is a normal and fairly constant form 

 of chlorophyll-corpuscle, yet other irregular forms appear 

 side by side with these. How can such irregular forms be 

 explained on the parasite theory ? They present no diffi- 

 culty if the corpuscles are regarded as products of the 

 animal's cell-protoplasm, for it may well be that such pro- 

 ducts should sometimes be incompletely formed or of 

 monstrous size and shape. 



The brown and blackish granules noted by Kleinenberg 

 as occurring both in H. viridis and in the " greenless" 

 varieties of Hydra are important (PI. XX, fig. 19). They 

 appear to result from the breaking down of the chlorophyll 

 bodies or their colourless representatives. 



Professor Jeffrey Parker, in his paper on the endoderm of 

 Hydra {' Quart. Journ. Micr. Sci.,^ vol. XX), has advanced 

 the view that these dark granular bodies are ingested food 

 particles in the course of digestion. In this view I cannot 

 agree. They appear to me to be undoubtedly in the case 

 of H. viridis connected with a degeneration of a chlorophyll- 

 corpuscle, and in H.fusca I am inclined equally to attribute 

 them to the formative activity of the cell-protoplasm. Similar 

 dark-coloured granules in the endoderm of Cordylophora and 

 other hydroids (probably also the very scarce black granules 

 in the endoderm of the Medusa Limnocodium, ' Quart. Journ. 

 Micr. Sci.' (vol. XXI, PI. VIII, fig. 1 h), are also to be 

 regarded as products formed by the cell, and not as ingested 

 particles. However, it is difficult to distinguish one kind of 

 *' dark granule" from another, and it is possible that some 

 such dark granules, observed in the endoderm-cells of 

 Hydrozoa, are really food particles which are undergoing 

 intra-cellular digestion. 



The representatives of chlorophyll-corpuscles in colourless 

 and olive green Htjdrm. — It is an open question as to 

 whether the white, brown, and orange-coloured specimens of 



