ZOOLOaY AND BOTANY, MICROSCOPY, ETC. 643 



evacuation of genital products, or that its cells, in place of being 

 excretory, have the function of providing a cementing mass for the 

 ova. 



Embryology of Balanus.* — According to M. N. Nassonow the 

 ovum divides vertically into two sub-equal segments, of which the 

 anterior forms the later ectoderm, whilst from the posterior and 

 granular segment is exclusively derived entoderm and mesoderm. 

 An amphigastnda is formed, the blastopore closes, and the entoderm 

 divides, beginning ventrally, to form a symmetrical plate of mesoderm. 

 The chief part of the mesoderm goes to form the three pairs of ventral 

 projections which are the rudiments of the limbs of the nauplius, and 

 does not take any share in the formation of the muscular system. 

 The anus is formed at the spot where the blastopore originally 

 occurred. 



Vermes. 



Oogenesis and Spermatogenesis in Branchiobdella.t — Dr. W. 



Voigt finds that the reproductive organs of BrancJiiobdella are formed 

 on the type of the OligochsBta ; the two ovaries are in the eighth 

 segment, and, even in living forms, are distinguishable by their 

 whitish coloration ; each consists of a compact mass of cells attached 

 to the septum by a muscular stalk ; the testes are found in the sixth 

 segment, but their stalk of attachment is not provided with muscular 

 tissue. During its development the cells of the ovary exhibit great 

 powers of multiplication ; the ova derive their nourishment from a 

 pair of vascular loops which extend from the dorsal to the ventral 

 trunk. 



In treating of spermatogenesis, the author makes use of the 

 terminology of La Valette St. George, who recognizes five stages — those 

 of the sexual cells, spermatogonia, spermatocytes, spermatids, and 

 spermatosomata. What Mr. Blomfield called the blastophor is here 

 called the cytophor. The sexual cells give rise to spermatogonia in 

 the ordinary way, and by indirect division of the latter to spermato- 

 germs. The author has been able to observe in both testes and 

 ovaries degenerated cells, the cause of which is often due to the 

 taking in of a large quantity of fluid. 



New Parasitic Leech.t — Dr. J. Leidy describes a new parasitic 

 leech infesting the mouth of the so-called Colorado pike (PtychocJiilus 

 lucius). From its conspicuous gland-like organs and habit, Dr. Leidy 

 proposes to name it Adenohdella oricola. 



Archenchytraeus M6bii.§— The structure of this new species is 

 briefly described by M. W. Michaelsen. The worm has about sixty 

 setse-bearing segments, and the seta) are aggregated in bundles of throe 

 to five. The testes are developed on the mesentery, separating 

 segments 10 and 11, the ovaries on the succeeding mesentery. The 



♦ Zool. Anzeij?., viii. (\Hm) pp. 193-5. 



t AH^^-it. Zwl. '/jx>i. IiiHt. Wurzburf,', vii. (1885) pp. 300-08 (3 pla.). 



t 8cictjce, V. (1S85) pp. AVA-h (I fl-,'.). 



§ Zwl. Aiizfig., viii. (1885) pp. 2;{7-9. 



