136 J- Moore, 



especially in a recent publication by Jnlin ^) on the spermato- and 

 ovo-genesis in Styelopsis grossularia, we find that the extrusion of 

 the polar bodies from the ovum (or the corresponding divisions in the 

 generation of the male element) is brought about by two successive 

 mitoses, or "pseudo-mitoses", in which, as Julin says, the achromatic 

 spindle is apparently wanting, and in which centrosomes are absent. 

 The complete manifestation of karyokinesis is thus not essential 

 to the reduction uf the supposed superfluoiis hereditary substance, or 

 whatever the extrusion of the polar bodies may represent, in connec- 

 tion with the primary equation of the male and female nuclei; and it 

 follows therefore that the same interpretation can be put on such 

 phenomena as the degenerate mitoses in the mammalian spermatogenesis 

 which I have just described. 



The origin of the spermatocytes. 



The nuclei of the elements which have become differentiated from 

 the primitive stock, and which may be said to represent the sperma- 

 togones, become very chromatic and show numerous condensations of 

 chromatin over their circumference. 



The longitudinal division (Fig. 1) itself is not very easy to catch. 

 When found, the chromosomes are long and slender, and so crowded that 

 their number, sixteen, can only be deduced on the average of many 

 readings. Previous to the longitudinal division there does not appear 

 to be any archoplasm in the spermatogones, its absence being probably 

 connected with their previously akinetic mode of fission; the daughter 

 elements wliich arise by their longitudinal division constitute the 

 she nuclei of the young growing cells of Brown, and I see no vital 

 objection to the use of the term "spermatocytes" when speaking of 

 these elements (Figs. 2, 3). 



In the rat, the whole spermatogenesis may be separated by the 

 longitudinal and the hetrotype mitoses into three periods; one, relating 

 to the growth and akinetic multiplication of the spore-cells, and 

 terminated by the longitudinal division; another, constituted by the 



1) Bull. Sci. de la France et de la Belgique. Tom. XXV. p. 1—60. 



