44 SUMMARY OF CURRENT RESEARCHES RELATING TO 



they usually sink into the blastoderm cavity, and degenerate when the 

 endodermic immigration occurs. 



The cleavage is total, approximately equal, and radially symmetrical. 

 A blastosphere of 128 cells is formed. The immigration of the primary 

 endoderm is started by a polar proliferation and localized "primary 

 delamiuation." The mid-gut appears as a gradually increasing vesicle 

 among the primary endoderm nuclei, cell-boundaries having become 

 indistinct. The remaining nuclei form the mesoderm nuclei. The 

 author describes the formation of the apical plate, the oesophagus, the 

 ventral nerve-cord, and so on, and compares the mode of development 

 in Gypris incongruens with that in other Entomostraca. Five types of 

 development are distinguished, depending chiefly on the amount of 

 yolk and on the way in which it is utilized. 



Thersitina gasterostei Pagenstecher.* — Robert Clurney has some 

 notes on this parasitic Copepod, the females of which occur in abundance 

 under the opercula of the stickleback, especially Gasterosteus aculeatus. 

 It is probable that, as in the nearly related Ergasilus, the female is 

 fertilized once and for all during the free-swimming stage. No males 

 were found below the operculum ; spermatophores have been seen 

 attached to a free-swimming female ; there is a large receptaculum 

 seminis : it is probable that spermatozoa remain alive within the female 

 for about five months ; it is probable that a mature female lays two, or 

 perhaps three, lots of eggs and then dies, giving place to a new genera- 

 tion ; there may be five generations within the year, overlapping to 

 some extent. The author describes the male for the first time. The 

 life-history is also described. 



Annulata. 



British Fresh-water Leeches.j — Henry Whitehead gives an account, 

 based on Harding's Revision (1911), of eleven species of Hirudinea 

 found i n Britain, and adds^notes of his own observations. 



Nematohelrmnthes. 



New Nematodes from Soil.J — N. A. Cobb gives the characters of no 

 fewer than twenty-six proposed new genera and of a type of each, found 

 in soils (fresh and non-brackish). Most of them are injurious to vegeta- 

 tion. Useful diagnostic tables are given, and attention must be called 

 to the ingenious way in which the author has been able to condense a 

 long paragraph of characters into a single line of formula with numbers 

 and signs. 



Vulvar Annulus in Nematode^ — L. Gr. Seurat describes in Mau- 

 pasiella weissi, a Nematode from the ctecum of Macroseelides, a peculiar 

 brown or black chitinoid annulus, about a millimetre in width, which 



* Ann. Nat. Hist., xii. (1913) pp. 415-24 (4 pis.). 



t Essex Naturalist, xvii. (1913) pp. 61-85 (2 pis.). 



% Joum. Washington Acad. Sci., iii. (1913) p. 432-44 (1 fig.). 



§ C.R. Soc. Biol. Paris, lxxv. (1913) pp. 326 30 (6 figs.). 



