:-504 SUMMARY OF CURRENT RESEARCHES RELATING TO 



shields, and Ophionotus, differing from Ophioglypha in the larger number 

 of arm-plates, and in the absence of incisions and spine-combs over 

 the bases of the arms. An interesting series of variations in Cytherea 

 simplex is noted. 



Coelentera. 



Spermatogenesis in Hydra and Aurelia.* — W. M. Aders describes 

 the development of the testes in Hydra viridis from accumulations of 

 sub-epithelial " indifferent " cells, which are not at first distinguishable 

 from indifferent elements which occur elsewhere. There is no histo- 

 logical evidence of a distinction between somatic and primitive germ- 

 cells. The cells forming the primordium of the simple testis multiply 

 and grow, and may soon be called spermatogonia. Their nuclei seem 

 distinctly larger than those of the other sub-epithelial cells, and their 

 plasma steins more darkly and intensely. As multiplication proceeds 

 two generations of spermatocytes may be distinguished ; they differ in 

 size, but the author was not able to count the chromosomes. He follows 

 the spermatocytes onwards to spermatids and spermatozoa. 



In the male gonads of Aurelia aurita, Aders found certain large 

 cells in the ripe follicles among the sperm-forming cells. It seems that 

 these are separated off from the endoderm, that they migrate into the 

 testes, and that they serve as nutritive cells for the seminal elements. 



Coelentera from Intermediate Waters of North Atlantic! — 

 K. T. Giinther reports on a collection obtained by Mr. George Murray 

 during the cruise of the ' Oceana' in 1898. Especially noteworthy is a 

 Leptomedusoid Laodice chapmani sp. n., differing from other species in 

 the character and distribution of the gonads, and an Anthomedusoid 

 Bythotiara murrayi g. et sp. n. — a Tiarid with four radial canals, which 

 bifurcate and open into the circular canal by eight adradial terminal 

 branches, and with four gonads arranged interradially along the manu- 

 brium. 



Porifera. 



Ingestion of Food-Particles in Sycandra raphanus.} — J. Cotte 

 fed this sponge with carmin and carbon particles, rice-starch, and 

 bacteria. The collar-cells or choanocytes were seen to form pseudo- 

 podium-like processes on their apical surface, and with these they en- 

 gulfed the particles which the flagellum swept towards them. In short, 

 an amoeboid mode of ingestion is confirmed. 



Metabolism in Sponges.§ — J. Cotte finds that the nitrogenous dis- 

 assimilation-products of Suberites domuncula are wholly or partially 

 amides. 



The juice of the same sponge turns brown on exposure to air. 

 This is due to tyrosinase, a tyrosin-forming ferment. Tyrosin is not 

 formed in the living sponge, but is produced by the digestive ferments 



* Zeitschr. f. wiss. Zool., lxxiv. (1903) pp. 81-108 (2 pis. and 8 figs.). 



t Ann. Nat. Hist., xi. (190:5; pp. 120-30 (2 pis.). 



% C.R. Soc. Biol. Paris, liv. (1902) pp. 1315-7. See Zool. Centralbl., x. (1903) 

 p. 177. 



§ C.R. Soc. Biol. Paris, liv. (1902) pp. 1317-8; lv. (1903) pp. 137-9, 139-41. See 

 Zool. Centralbl., x. (19(»3) pp. 177-8. 



