316 SUMMARY OF CURRENT RESEARCHES RELATING TO 



nnd the sperm duct. The chromosomes preserve their individuality 

 from the time when reduction in number occurs in the very young 

 oocytes to their appearance as tetrads in the first polar spindle. The 

 scattered chromosomes of the germinal vesicle are collected by currents 

 in the karyoplasm, at the point where the first polar spindle is formed. 

 There is a preliminary longitudinal splitting of the chromosomes during 

 their reduction in size. The chromosomes in the young oocytes conjugate 

 longitudinally, instead of end to end as in the spermatocytes ; there are 

 two types of conjugation of the chromosomes — oocyte and spermatocyte, 

 and two corresponding types of maturation divisions, giving, however,, 

 equivalent results. The chromatin (?) granules which result from the 

 reduction in size of the chromosomes pass directly out from the nucleus, 

 into the cytoplasm along strands of karyoplasm. 



Nematohelminth.es. 



Freshwater Nematodes of New Zealand.* — X. A. Cobb describes, 

 four new free-living species — M&rmis Nova Zealandm, Mononchus rex, 

 Dorylaimus Nov<z Zealandim, and D. profundus. These belong to well- 

 known genera, and present no remarkable variations from the types of 

 their 'respective groups. It is probable that many of the free-living 

 genera have a very wide geographical distribution. The small size of 

 the individuals, their fecundity, their adaptability to transportation by a 

 great variety of agencies, and their resistance to desiccation, at least in 

 certain stages, are all in favour of wide distribution. A noteworthy 

 point is the depth from which some of the specimens were captured j 

 thus the two species of Dorylaimus were obtained from 200-1100 feet. 



New Free-living Nematode from Patagonia \ — J. G. de Man 

 describes a new form, Phctris (Plectrotdes) patagonicus, which differs, 

 from P. antarcticus in form, in structure of head lips, and of oesophageal 

 bulb. The type specimen was found in a dung-ball of Grypotherium 

 darwini. 



Ichthyonema grayi.} — James F. Gemmill gives an account of 

 IcMhyonema grayi Gemmill and von Linstow, an interesting Nematode 

 of large size found in the perivisceral cavity of the common sea-urchin 

 in different localities in the Firth of Clyde. Not more than four 

 females (600-1500 mm. in length by 2-4 mm. in breadth) occurred in 

 any one sea-urchin, and in one case only a single large specimen was. 

 present, which measured quite five feet in length. Besides the large 

 specimens, some smaller ones were always present, 50-200 mm. in length, 

 which seem to be the males. A full description has been published else- 

 where §, and we may simply refer to some notable features : — the 

 absence of mouth, anus, and excretory canals ; the poorly developed 

 muscular system ; the simplicity of the nervous system, represented by 

 a thickening of the hypodermis at the head end, which is not continued 

 backwards into definite longitudinal cords, except, perhaps, for a short. 



* Proc. Cambridge Phil. Soc.xii. (1904) pp. 363-74 (4 flgs.). 

 t Ber. Senck. Natur. Ges. (1904) pp. 41-5. 

 % Trans. Nat. Hist. Soc. Glasgow, vi. (Dec. 1903) pp. 299-301. 

 § Arch. Natur., 1902. 



