Some Points in the Spermatogenesis of Mammalia. 137 



«growth and division of the spei-matocytes, and terminated by the hetro- 

 type division; and a third, formed by the conversion of the daughter 

 elements (which we may term spermatids) directly into the sper- 

 matozoa. 



In the dog, I am not sure whether the longitudinal division exists; 

 it may of course liaA^e become so modified as to be indistinguishable 

 from the preceding akineses, but whether this is so or not, it foUuws 

 that the division into three periods, although convenient, is not univer- 

 sally applicable to all mammals. In whatever manner the spermatocytes 

 may have arisen, their nuclei are at first exceedingly chromatic, the 

 chromatin being, aggregated into a close network of thick fibres, while 

 at one side there usually lies the prominent nucleolus desci'ibed and 

 figured by Hermann, 



General consideration of the attraction sphere. 



As soon as the long pro-phases of the final karyokineses set in 

 among the spermatocytes, and often long before, their cell bodies present 

 a well marked and slightly staining archoplasm. This structure in the 

 rat, as in other mammals, appears to be derived ù'om a coalescence 

 of the spindle fibres of the previous division, i. e. it beai's the same 

 relation to the spindle fibres as the great Nebenkern described by 

 Platner in the spermatocytes of Helix. 



A short time ago I found') the immense archoplasm of the cells 

 of the genital ridge of the larval salamander to have a similar origin, 

 and I then ventured to predict that wherever the archoplasm existed 

 at all, Platner's remark that"-) „zwischen Knäuelgerüst, Spindelfasern und 

 Nebenkern, ein genetischer Zusammenhang existirt" would be of uni- 

 versal application. 



At the time I wrote I supposed the centering of the spindle 

 or rather intrazonal fibres about the intermediate body, occasionally 

 seen in the undiiferentiated genital ridge of the Salamander, to be the 

 rule rather than the exception. Dr. Meves has since most Idudly drawn 

 my attention to some later and more elaborate results of his own, 



^) Cf. Qu. Jour. Micros. Sci. Vol. XXXIV. p. 181—196. 

 -) Archiv für mikr. Anat. Bd. XXVI. p. 604. 



