498 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Swedish forms. Of the 9G species recorded from Sweden we have 75 in? 

 Britain, or known to occur in Britain, and there are six British species, 

 which are not given by Lilljeborg as Swedish. Scourfield gives a clear 

 table showing the general distribution of the British species of Cladocera. 



Annulata. 



Revision of Annelids of the Cette Region.* — A. Soulier has begun 

 an arduous task, and gives revised descriptions with synonymy, &c, of 

 Amphiylene mediterranea, Oria armandi, Spirograph^ spallanzanii, Pota- 

 milla reniformis, Myxicola infundibulum and M. cesthetica, Pomatoceros 

 triqueter, Serpida crater, Hydro ides uncinate, and Protida meilhaci. The 

 precise and terse diagnoses may be of service to those working at this 

 class of Annelids. 



Artificial Parthenogenesis in Egg of Podarke obscura.j — A. R. 

 Treadwell subjected unfertilised ova of this chretopod to sea-water plus 

 potassium chloride, and then returned them to normal sea-water. The 

 results were various. Some exhibited " pseudo-cleavage," in which the 

 cytoplasm divided though the nucleus did not. In some cases the 

 chromatin was irregularly diffused, and often a large number of astro- 

 spheres were seen in the cell. Other ova exhibited both nuclear and 

 cytoplasmic cleavage. But neither the pseudo-cleavages nor the true 

 cleavages followed the typical schema of the normal segmentation. No 

 polar bodies were formed. 



Ciliated " embryos " arose after or without true cleavage, and in both 

 cases a prototroch was formed. Coalescence of ova and embryos was 

 observed, but not so markedly as in Chcetopterus. 



Phenomena of Fertilisation in HEementeria costata.f — A. Kowalev- 

 sky has added details to his previous account of the remarkable processes 

 of fertilisation in this leech. The male genital aperture does not lead 

 directly to the gonads but into an intermediate cavity into which the 

 spermatophore-sac opens and in which the anterior end of the sperma- 

 tophore is received. "When the spermatophore is introduced into the 

 male aperture, its anterior end perforates the posterior wall of the above- 

 mentioned cavity, and the spermatozoa liberated into the cavity of the 

 body accumulate in the space between the spermatophore-sac, the ovaries, 

 and the " matrix." 



When the whole contents of the spermatophore have been liberated,, 

 the empty sac is detached from the body and falls off. The spermatozoa 

 are in many cases destroyed by the cells of the nephridial capsules or 

 other phagocytic elements, but a certain number penetrate through the 

 matrix and get into the ovaries. 



Oogenesis and Spermatogenesis in Sagitta bipunctata.§ — 1ST. M. 

 Stevens finds that the points of special interest in the oogenesis of 

 Sagitta are : (1) the unbroken continuity of the reduced number of 



* Mem. Acad. Sci. Montpellier, iii. (1902) pp. 109-63 (10 figs.). 



t Biol. Bull. Mar. Biol. Lab. Woods Holl, iii. (1902) pp. 235-40 (12 figs.). See 

 Zool. Centralbl., x. (1903) p. 116. 



J Mem. Acad. Imp. Sci. St. Petersbourg, xi. No. 10 (1901, received 1903) pp. 19- 

 (1 pi.). § Zool. Jahrb., xviii. (1903) pp. 227-40 (2 pis.). 



