Some Points in the Spermatogenesis of Maimnalia. ]63 



tions-Teilung" but if so, the case becomes much worse, because then 

 there would be manifestly no final nuclear equation among mammals, 

 and it follows that the „Reductions-Teilung" would not be essential 

 to fertilization, — in fact, it seems to me that this conclusion follows 

 in either case. 



The incorporation of the archosome into the spermatozoon is a 

 matter of considerable theoretical importance, because it has long 

 been known that in the less specialized spermatozoa a residuum of 

 cytoplasm is always carried over with the male element into the 

 ovum, during fertilization; but in many of the tailed forms this does 

 not appear to be the case. In those which exhibit a marked „Mittel- 

 stück" this structure has generally been found to be constituted in 

 part, if not entirely, by the archoplasm (cf. Field, Anat. Anz. Bd. VIII. 

 p. 487). Lastly, in the type we are considering there is, i)roperly 

 speaking, no „Mittelstück", its position being occupied apparently by 

 the centrosomes and intermediary bodies, while the archosome which 

 was a derivative of the archoplasm, which was a derivative of the 

 spindle-fibres, which are generally derivatives in part, if not wholly 

 derivatives of the cytoplasm, becomes a cephalic cap for the sper- 

 matozoon. So that the positions of the cytoplasmic derivative and the 

 centrosomes, when compared with those of the echinoderms and pro- 

 bably other animals, appear to be reversed. 



There are some other considei-ations with respect to the position 

 of the archosomes in mammals, which though probably not of much 

 value, may be stated for what they are worth. In the ripening 

 spermatozoa of Styelopsis, Julin describes the appearance of a small 

 refractive particle, ultimately destined to sit at the cephalic point in 

 the spermatozoon. In fertilization this particle assumes the character 

 of a centrosome with radiations, and is called the "spermocentre". 

 Field, in his researches on echinoderms, has followed the spermatid 

 centrosome to a final position also at the apex of the spermatozoon 

 head. Now, Fol's observations on the "central quadrille" in Asterias, \) 

 and more recently those of Fick on the Axolotl, show that the centro- 



') Cpt. Rendus. T. CXII. p. 877. 



11 



