640 SUMMARY OF CURRENT RESEARCHES RELATING TO 



picta sp. n. is discussed at some length. The new genus Megaluropus 

 should not be placed, as it has been by Dr. Hoek, among the Parda- 

 liscidse. 



Spermatogenesis in Ostracoda.* — Dr. G. W. Miiller finds that the 

 mother-cells of the spermatozoa of Ostracods are matured in the middle 

 of the testicular tubes {Pontocypis) or at their ends (Fresh- water 

 Cyprids). These mother-cells either migrate as needed, when a testi- 

 cular tube always contains spermatozoa of the same age and mother-cells 

 of only two or three sizes {Pontocypris, Cypris compressa), or a large 

 number migrate during youth and before the formation of the sperma- 

 tozoa. The mother-cells increase in size from before backwards ; in 

 Cypris dispar, Gaudona, and Notodromas we always find spermatozoa and 

 mother-cells of very various ages and sizes. The number of cells which 

 divide at one time varies in Pontocypris sp. between three and nine, in 

 Cypris compressa between three and eight ; in G. dispar it is two, and 

 in Notodromas and Gaudona four. Each mother-cell ordinarily gives 

 rise to four sperm-cells, and only occasionally to three or two. 



True spermatogenesis is effected in very much the same way as in 

 other Arthropods. One or two subsidiary nuclei form a tail-piece which 

 grows to an extraordinarily great length, and is of a very complicated 

 structure ; the nucleus is either placed quite at the end of the body so 

 formed (^Pontocypris) or near the end (Fresh-water Cyprids). The part 

 formed by the subsidiary nucleus is divided into a broader and a narrower, 

 portion or head and tail. As the spermatozoa are variously arranged 

 in the testis, and as the complicated apparatus of the efiierent ducts 

 require a similar arrangement of all the spermatozoa, it is clear that 

 some of the spermatozoa must be turned round. In Pontocypris this is 

 effected by those which go out with the tail forwards, passing into a 

 csecum, while they, of course, leave with their heads directed forwards. 

 In the fresh- water Cyprids all the spermatozoa pass into the csecum, 

 and so are all turned round ; those that need to be turned the other way 

 enter a pyriform enlargement of the vas deferens which lies between the 

 testis and the caecum. 



The spermatozoa consist of the central filament and three bands 

 which lie beside one another, and are connected with one another along 

 their whole length ; of these the median band is contractile. A con- 

 ti action of this band causes the spiral twisting. The investment of 

 some species is secreted by the spermatozoon itself, while in other cases 

 it is possible that the investment is secreted by the walls of the vas 

 deferens. In one case (Pontocypris) at least we can certainly prove that 

 the investment contracts, and that very strongly; in the fresh-water 

 Cyprids the contraction is probably slighter. This contraction probably 

 aids the spermatozoa in escaping from the receplaculum seminis. 



New Pelagic Copepods.f — Dr. W. Giesbreeht gives a list of the 

 pelagic species of Copepoda collected on the voyage of the ' Vettor 

 Pisani' (1882-5), and by F, Orsinifrom the Eed Sea. The list includes 

 63 species, of which 41 are new. The latter are briefly diagnosed. 

 Nine new genera, Acrocalanus, Galocalanus, Leptocalanus, Clausocalanus, 

 Ctenocalanus, Spinocalanus, Gaetanus, Undeuchsela, and Euchirella, are 

 distinguished. 



* Zool. Jabrb. (Abtb. f. Anat.), iii. (1889) pp. 677-726 (2 pis.). 

 t Atti K. Accad. Lincei (Reudic), iv. (1888) pp. 330-8. 



