154 SUMMARY OF CUERENT RESEARCHES RELATING TO 



hold a small animal until the manubrium is extended beyond the margin 

 of the umbrella and applied to the object. No swimming was observed. 

 The genus is distinguished from Eleutheria and from Cladonema, and the 

 following outstanding features are noted : The medusa is adapted for 

 crawling or walking ; there is no brood pouch above the stomach ; the 

 gonads are well developed and lie in ectodermal inter-radial pockets around 

 the stomach ; the sexes are separate ; the radial canals are usually six ; 

 the tentacles are numerous, increasing with age, not corresponding to 

 the number of radial canals, the upper branch with several clusters of 

 nematocysts in addition to a terminal cluster ; there are no oral tentacles ; 

 there is a thick nematocyst ring under the margin of the bell ; the hydroid 

 has one verticil of three capitate tentacles, and a second verticil of six non- 

 capitate tentacles ; the hydroid form is very similar to that of Cladonema 

 (Stauridia), not to that of Eleutheria (ClavateUa). J. A. T. 



Porifera. 



Study of Fresh-water Sponges. — A. van Trigt (Leiden, 1919, 

 15 pp., 6 pis.). This study is based on grass-green and colourless forms 

 of Spongilla lacustris and Ephydatia fluviatilis, two kinds readily dis- 

 tinguished by the pungent smell of the former. The sponge owes its 



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y 



4 



Capture of food particles by cells of choanocyte layer. 



green colour to numerous green corpuscles present in the cells, especially 

 in the amcebocytes. They produce oxygen and exhibit photosynthesis 

 in the light ; they show^ a cell- wall, protoplasm, a chloroplast, and perhaps 

 a nucleus ; they contain oil-drops, but no carbohydrates ; they can live 

 for six months or longer isolated from the sponge, and they can multiply 

 after isolation ; they also occur free in the water. It may be safely 

 concluded that they are symbiotic Algte. They multiply by the division 

 of the whole cell, and are nearer to Fleurococcus than to Chlorella. 



