176 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Determination of Sex in Daphnids.* — Alexander Issakowitsch com- 

 bats the view that the appearance of amphimixis in the course of the 

 parthenogenetic generations is only indirectly correlated with external 

 conditions. He has made experiments with Simocephalus vetulus 0. F. 

 Miiller, and these lead him to the conclusion that nutrition and tempe- 

 rature (by affecting nutrition) are the determining factors in the con- 

 tinuance or interruption of the parthenogenesis. There is no cyclic 

 sequence of events in Weismann's sense. 



Alaskan Amphipods.| — S. J. Holmes reports on 22 species of 

 Amphipods collected by the Harriman Alaska Expedition. The follow- 

 ing are new : — Tryphosa nugax, Stenothoe alaskensis, Gammaropsis 

 tenukomis, Caprella alaskensis, G. scabra, G. kincaidi. 



Pycnogonids of the West Coast of North America.! — Leon J. 

 Cole, in reporting on the Harriman and other collections, gives a useful 

 discussion of the confusing terminology of the external features. 

 Thirteen species are dealt with, of which the following are new : — ■ 

 Lecythorhynchus marginatus, Tanystylum intermedium, 6 species, Glotenia 

 occidentalis, Halosoma viridintestinalis g. et sp. n., Anoplodactylus erectus. 



Regeneration in Polychsets.§ — J. Nusbaum gives a detailed account 

 of the regenerative processes in Amphiglene mediterranea Leydig and 

 Nerine cirratulus Delle Ch. He deals especially with the closure of the 

 wound at the posterior or anterior end of the body, the regeneration of 

 the posterior or anterior gut, the regeneration of the cerebral ganglion, 

 of the oesophageal commissure, of the ventral cord, of the longitudinal 

 and circular musculature of the blood system, and of the parapodia. He 

 shows that Weismann's adaptive theory of regeneration is so far useful, 

 but that it does not suffice to cover the facts. 



Artificial Parthenogenesis in an Annelid. || — G. Bullot has reared 

 free-swimming larvas of Ophelia from artificially parthenogenetic ova. 

 The mixture used was 2 c.cm. 2 \ n KC1 + 88 c.cm. sea-water. After two 

 hours the first cleavage was completed ; after five hours there were 

 blastulas, which soon began to swim a little. From 20-60 p.c. of the 

 artificially parthenogenetic ova became larvae, but none lived longer 

 than two days. Contrary to Lillie's results, the segmentation appeared 

 to be quite regular. 



Regeneration in Lumbriculus variegatus.H" — F. von Wagner finds 

 that the restoration of the head end depends on the proliferating and 

 formative power of the epidermis, aided by the epithelium of the gut, 

 and by the activity of special elements, the " neoblasts." The repair of 

 the alimentary tract precedes that of the nervous system. 



The proliferations of the epidermis show three stages : first there 



* Biol. Centralbl., xxv. (1905) pp. 529-36. 

 t Harriman Alaska Expedition, x. (1904) pp. 233-46 (11 figs.). 

 % Tom. cit., pp. 249-98 (16 pis.). 



§ Zeitschr. wiss. Zool., lxxix. (1905) pp. 222-307 (4 pis. and 1 fig.). 

 || Arch. Entw. Mech., xviii. (1904) pp. 116-70 (13 figs.). See also Zool. Zentralbl., 

 xii. (1905) pp. 435-6. 



f Zool. Jahrb, xxii. (1905) pp. 41-156 (5 pis.). 



