310 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



females, on the contrary, when they leave the capsule, are still in the 

 larval state. But before they leave the capsule they are inseminated by 

 the small males. This is one very remarkable feature, and another is 

 that the maturation-division, in the case of the female-producing eggs, 

 takes place after, not before, fertilization, which seems contrary to all 

 known rule. The presence of large eggs, which invariably give rise to 

 females, seems to be due to fertilization ; the unfertilized eggs remain 

 smaller and give ri«e to males. The male-producing egg has a single 

 nucleus, the female-producing egg has for a time a double one— one 

 portion being derived from the sperm. Two polar bodies are given off 

 by both the male-producing and the female-producing egg, and the 

 number of chromosomes (20) is the same in both. 



Nervous System of Hirudinea.* — G. Ascoli has made a study of the 

 minute structure of the nervous system. He deals first with the struc- 

 ture of the nerve-fibres, and finds clear evidence of the occurrence of a 

 neuro-fibrillar network around the axis cylinder. He gives a detailed 

 account of the sympathetic system in which the elements are very closely 

 bound together by the plasmic coalescence of processes and by the union 

 of fibrils from different cell-areas. 



Nematohelminthes. 



Maturation and Fertilization in Ascaris megalocephala.t — E. 

 Faure-Fremiet discusses the various substances observed in the much- 

 studied germ-cells of this threadworm. The oocytes show (1) mitochon- 

 dria formed of an albuminoid basis and a phosphatid body allied to 

 lecithin ; (2) fatty bodies with angular and irregular contours, probably 

 some kind of wax ; and ('6) vacuoles containing glycogen. The young 

 stages in the spermatogenesis show a neutral fat in the cells ; the later 

 stages show mitochondria like those of the oocytes and van Beneden's 

 " brilliant granules," which are globules of some albuminoid. 



In fertilization, the " brilliant granules " dissolve, and the contained 

 albuminoid lessens the surface tension of an alkaline solution. This is 

 manifested in the ovum by a disturbance of the equilibrium of the cyto- 

 plasmic emulsion. The glycogen vacuoles fuse and move to the surface. 

 Part of the glycogen is transformed and chitin is formed in the vacuoles. 

 The chitin is deposited as the external membrane. A saponification of 

 the waxy substance occurs and an internal membrane is formed by 

 coprostearin moving to the surface of the egg. 



Spiroptera sexalata Molin.J — Joan Ciurea describes this small 

 Nematode, with triple lateral " wings," which Molin separated off from 

 S. strongylina Rudolphi. Both occur in the pig's stomach. Ciurea 

 compares S. sexalata with Filaria nitidulans Schneider from the 

 American Tapir, and shows that the two are distinct. He proposes that 

 both should be referred to Diesing's genus Physocephalus. 



* Zool. Jahrb., xxxi. (1911) pp. 473-96 (4 pis.). 



t Bull. Soc. Zool. France, xxxvii. (1912) pp. 83-4. 



I Zool. Jahrb., xxxii. (1912) pp. 285-94 (1 pi. and 2 figs.). 



