100 RECORD OF CURBENT RESEARCHES RELATING TO 



digestion, being so large as nearly or quite to obliterate the digestive 

 cavity. 



Mr. Parker also suggests an explanation of the dark, greenish or 

 brownish granules formed in the endoderm cells of all species of 

 Hydra, He considers that these are solid food particles, derived 

 from the alimentary canals of the prey, so that Hydra presents the 

 characteristically protozoan mode of digestion, observed by Metsch- 

 nikoff in Turhellaria and in sponges,* In one case, a diatom 

 frustule was found embedded in the protoplasm of a cell. 



Nematocysts were observed in the endoderm : this is another 

 argument against Kleinenberg's view that only interstitial cells act as 

 mother-cells of the nematocysts. 



4. Methods. — For ordinary sections, Kleinenberg's picric acid is 

 recommended, the animals being first killed with hot water : for 

 demonstrating the relations of the muscular fibres the specimens were 

 placed alive in ammonic bichromate, 1 per cent., this reagent causing 

 a slight separation of the layers. In both cases they were afterwards 

 treated with alcohol of gradually increasing strength. Cacao butter 

 was used as an embedding material. 



For showing the cilia of the endoderm cells, the specimens were 

 placed alive in 1 per cent, osmic acid, kept in it for twenty-four 

 hours, and then transferred to equal parts of glycerine and water. 

 Sections of these were cut by the freezing method. 



For demonstrating the supporting lamella, and for teasing purposes 

 generally, acetic or osmic acid or ammonic bichromate answered 

 best. 



Early Development of Gonothyrasa Loveni.t — R- S. Bergh, of 

 Copenhagen, has a long paper on this subject. The following are 

 his most important results, 



1. Development of the Egg. — The egg of Gonothyrcea arises from a 

 single endoderm cell ; the yolk is differentiated into hyaline ecto- 

 plasm and granular endoplasm. There is no investing membrane. 

 The germinal vesicle is spherical, and situated in the centre of the 

 egg; it is surrounded by a distinct membrane, and contains a net- 

 work of nucleoplasm, in the centre of which is the single germinal 

 spot : the latter contains a vacuole. 



As the egg grows, addition of new matter takes place only in the 

 endoplasm and in the germinal vesicle, not in the ectoplasm. The 

 nucleoplasm becomes dissolved in the nuclear fluid, and the germinal 

 spot undergoes division. Gradually the distinction between ecto- 

 plasm and endoplasm disappears ; the germinal vesicle assumes a 

 peripheral position, probably by means of the amoeboid movements of 

 the yolk ; the germinal spots, after repeated division, become dissolved 

 in the nuclear fluid. By this time both egg and germinal vesicle 

 have considerably increased in size. 



The next change is the disappearance of the membrane of the 

 terminal vesicle, its contents mingling with the surrounding yolk : 

 the growth of the egg is now complete. Next the characteristic 



* See thia Jouruul, ii. (1879) v\u 287 and 894. 

 t ' Morphol. Jahrbufb,' v. (1879) p. 22. 



