Some Points in the Spermatoja^enesis of Mammalia. 145 



them particularly difficult to find, in such an element as (ii'ig. ò) 

 however, the whole original contour of the nucleus may still be seen as 

 a light space in the cytoplasm, while the chromatic loops lie in an 

 irregular heap about the centrosomes (c). By the continued divarication 

 of the centrosomes, the spindle figure now gi'adually forms, the chromatic 

 loops withdrawing to the equatorial region of the cell, until, at last, 

 they stand stiifly out at right angles to the spindle axis (V\g. 6). 



Very soon however they begin to be crushed down and flattened 

 out along the surface of the spindle (Fig. 7, 8), going thi'ough the 

 usual hetrotype metamorphosis, until the long closed loops finally divide 

 in the equatorial plane, first on one side and then on the other, the 

 V-shaped daughter chromosomes collecting about the centrosomes to 

 form the daughter nuclei (Figs. 7, 8, 9, 34). 



1 have not observed the chromatic V's to become individually 

 duplicated at the close of the spindle figure, the tightly coiled mass 

 which they form rapidly passes, by disintegration and anastomosis of 

 the individual fibres, into a fine and intensely chromatic reticulum, 

 peculiarly characteristic of the spermatids when first formed. 



The centrosome. 

 In a recent article in the American Journal of Morphology Watasé 

 makes ^) an interesting attempt to theoretically solve the homologies 

 of the centrosomes, by supposing them to be simply accentuated cyto- 

 microsomes. While formulating the premises from which he arrives 

 at this conclusion, he assumes the staining capacity of the centrosomes 

 to be that of the chromatin or the microsomes; but unfortunately I do 

 not think that my own observations, any more than those of other 

 recent investigators (notably of Julin), can be brought into accord with 

 this view. The first and obvious objection lies in the extreme difficulty 

 with which centrosomes can be got to take a stain at all. If centi'O- 

 somes in general were of the same stuff as the chi^omatin (microsomes) 

 they ought to be best differentiated by pui-ely nuclear stains, and a 

 colour like methyline violet, which gives perhaps the most beautiful 



') Homology of the Centrosome. Loc. cit. Vol. VIII. p. 433—443. 



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