APPENDIX 209 



2. Atrn'tosis in the Early Sex-Cells 



Whether the progenitors of the germ-cells ever divide amitotically is a question 

 of high theoretical interest. Numerous observers have described amitotic division 

 in testis-cells, and a few also in those of the ovary. The recent observations of 

 Meves (91), vom Rath ('93), and Preusse C95), leave no doubt whatever that 

 such divisions occur in the testis of many animals. Vom Rath, however, maintains, 

 after an extended investigation, that all cells so dividing do not belong in the cycle 

 of development of the germ-cells ("93, p. 164) : that amitosis occurs only in the sup- 

 porting or nutritive cells (Sertoli-cells, etc.), or in such as are destined to degenerate, 

 like the -residual bodies"' of Van Beneden. Aleves has, however, produced strong 

 evidence ("94) that in the salamander the spermatogonia may, in the autumn, divide 

 by amitosis, and in the ensuing spring may again resume the process of mitotic 

 division, and give rise to functional spermatozoa. On the strength of these observa- 

 tions. Flemming ('93) himself now admits the possibility that amitosis may form 

 part ot a normal cycle of development, and Preusse has recently shown that amitosis 

 may continue through several generations in the early ovarian cells of Hemiptera 

 without a sign of degeneration. 



LITERATURE. V 



Van Beneden, E. — Recherches sur la maturation de Toeuf, la fecondation et la 



division cellulaire : Arch. Biol., \W . 1883. 

 Boveri, Th. — Zellenstudien. I., III. Jena, 1887-90. See also " Befruchtung " 



(List IV.). 

 Brauer, A. — Zur Kenntniss der Spermatogenese von Ascaris megalocepJiala : Arch. 



jiiik. Aiiat., XLII. 1893. 

 Id. — Zur Kenntniss der Reifung der parthenogenetisch sich entwickelnden Eies 



von Artcmia Saliiia : Arch. mile. Aitaf., XLIII. 1894. 

 Hacker, V. — Die \'orstadien der Eireifung (General Review) : Arch. inik. Atiat., 



XLV. 2. 1895. 

 Hertwig, 0. — Vergleich der Ei- und Samenbildung bei Nematoden. Eine Grund- 



lage fiir cellulaire Streitfragen : Arch. mile. Anal., XXXVI. 1890. 

 Mark, E. L. — (See List IV.) 

 Plainer, G. — tJber die Bedeutung der Richtungskorperchen : Biol. Centralb., VIII. 



1889. 

 vom Rath, 0. — Zur Kenntniss der Spermatogenese von Gryllotalpa vulgaris : 



Arch mik. Anal.. XL. 1892. 

 Id. — Neue Beitrage zur Frage der Chromatinreduction in der Samen- und Eireife : 



Arch. mik. Aiiat., XLVI. 1895. 

 Ruckert, J. — Die Chromatinreduktion der Chromosomenzahl im Entwicklungsgang 



der Organismen: Ergebn. d. Anat. u. Ejitwick., III. 1893 (1894). 

 Strasburger, E. — Uber periodische Reduktion der Chromosomenzahl im Entwick- 

 lungsgang der Organismen : Biol. Centralb.,XlW 1894. 



