STUDIES OF JJEPRODUCTIVE ELEMENTS: II. 35! 



Innern des Keimbläschen ??, welches hier übrigens von geringer Grösse 

 isr, angelegt wird, so lange noch die Kerimiembran vorhanden ist. 

 J)ie Annahme, dass in diesem Fall Protoplasma von aussen iji den 

 Kernraum hineingedrunuen sei, will mir wenis^stens als eine o-ezwuno-- 

 ene erscheinen." While thus the views of Straslmrger and Hertwig 

 are quite di Itèrent as to tlie oi-igin of the spindle fibres, the former 

 deriving tlieni from the cvt(^plasm and the latter from the nucleo- 

 plasm, the opinions of Flemuiiiuj (12, p. 75), Plainer (29, p. 70), 

 and othei-s stand midway between, since according t(3 these authors 

 the eijuatorial part of the spindle is formed from the nncleoj)lasm, 

 and the polar parts from the cytoplasm. The late investigation 

 by AiKjust Brauer (4^ of the spermatogenesis of Ascaris megaloce- 

 phala is very interesting on this point, inasmuch as the origin of the 

 spindle fibres is different in two varieties of the same species, fn 

 Ascaris megalocej)ha la uni Valens the centrosome is found in 

 the micleus, and there forms a small spindle which this authoi- com- 

 pares with the central spindle of Heriiianii, although the origin of 

 that is ditferent, as will be shown later on. In Ascaris mes-alo- 

 cephala bi va lens, on the other hand, the centrosome is first found 

 in the cytoplasm, closely attached to the nuclear w^all. By the divi- 

 sion of this is also formed a small spindle lying first tangentially to 

 the surface of the nucleus. Init the two centrosomes gradual Iv separate 

 from each other until they come to lie diameti-icallv opposite to each 

 other. What becomes of the central spindle fibres is not known, but 

 the author is inclined to think that these are divided in the separa- 

 tion of the centrosome (4, p. 181). 



Of no less interest than the al)ove are the observations oï Herman ii, 

 the result of whose investigation on the spermatocytes of Sa I am a n- 

 dra maculata, specially directed to the study of the origin of the 

 spindle fibres, nnnarkably accoi'ds with that of mine upon the 



