4. Fortpflanzungslehre. 365 



Sperma von Chaetopterus, als auch das der eigenen Art, die Eier der Echi- 

 niden zur Membranbildung anregt, ließ Verf. ein Gemisch von Sperma von 

 Chaetopterus und Sphaerechinus auf die Sphaerechinuseier einwirken. Unter 

 dem Einfluß dieses Gemisches bildete kein einziges Ei eine Dottermembran. 

 Es scheint sich daher in diesem Gemisch der Spermen weit voneinander 

 stehender Tierklassen eine antagonistische Wirkung zu äußern, welche die 

 Befruchtung nicht gestattet. Bruno Kisch (Prag). 



1008) Meek, C. F. V., The spermatogenesis of Stenobothrus viri- 

 dulus; with special Reference to the heterotropic chromosome 

 as a sex Determinant in Grasshoppers. 



(Journ. LiDnaean Soc. Zoology 32,211. p. 1—22. 3 plates. 1911.) 

 A detailed account of the spermatogenesis of this grasshopper. The chro- 

 mosomes are recognisable by their size and shape, and although they disappear 

 as such in the resting nuclei (with the exception of the heterotropic chromo- 

 some in the primary spermatocyte), they reappear in recognisable form at the 

 next division. The spermatogonial number is 17, the 4 th largest being the 

 heterotropic. It passes over undivided at the first spermatocyte division, and 

 hivides at the second. Half the secondary spermatocytes and spermatids thus 

 have 9, half 8. Doncaster (Cambridge). 



1009) Agar, W. E. (Glasgow University), The Spermatogenesis of 

 Lepidosiren paradoxa. 



(Quart. Journ. Micr. Sc. 57,1. p. 1—44. 5 plates. 1911.) 

 Lepidosiren offers peculiar advantages for the study of spermatogenesis 

 from the large size of the nuclei and chromatin. The material was collected 

 for the purpose of this study by the author in Paraguay, and the nuclei are 

 so large that he was able to make, in addition to thin sections, thick sec- 

 tions (35 — 40 fi) in celloidin, in which entire nuclei could be examined with 

 an immersion lens and stereoscopic eye-piece. The sections were also mount- 

 ed so that the same nucleus could be examined from both sides. The results 

 are of great interest. The somatic number of chromosomes in 38, two being 

 much largers than the rest. The reduced number is 19. The spermatogonia 

 occur in clumps at the ends of the testis-tubules; the nuclei have chromatin 

 in masses connected by Strands. In the earlier spermatogonia the nuclei often 

 are diffusely stained, and not infrequently are lobed, but no evidence of ami- 

 tosis was found. The later spermatogonia have smaller nuclei; they never 

 show diffuse staining nor are they lobed. These undergo a growth phase and 

 become primary spermatocytes with chromatin in a fine meshwork. In the 

 prophase of the first spermatocyte mitosis the stages are passed through des- 

 cribed by von Winiwarter as leptotene, zygotene, pachytene (bouquet stage) 

 leading to the stage of synizesis (Mac Clung). The author gives evidence 

 that the zygotene stage is produced by parallel conjugation of distinct chro- 

 matic threads. In the pachytene stage the number of loops cannot usually be 

 counted, but in one nucleus it could be determined with certainly that there 

 were about 19 horseshoe-shaped loops (the reduced number). Between the 

 pachytene stage and synizesis occurs a strepsitene stage, in which the longi- 

 tudinal halves of the pachytene thread separate again except at their ends, so 

 that the threads are converted into long rings. The halves of the rings then 

 break apart at one point of attachment, giving the reduced number of open 

 loops, and then separate at the other point of attachment so as to produce 

 the somatic number of Single chromosomes. Each of these Univalent chromo- 

 somes becomes shortened and constricted in the middle; the nuclear membrane 



