'I'lii: ilclcniiitiiilioii III' si'X ill ;iiiiiii:il ilcvclnjiiiiifiit. 749 



The only logical conclusion would ;ii)))ca,r to be, thîit the reduction 

 is the outward manifestation of the det(!rinination of sex. VMiether 

 the latter be brought to pass by the reduction of chromosonies, or, 

 as is quite possible, the reduction in the number be a cons(!(|uence 

 of the determination of sex; which of these be the cause and which 

 the effect is a (|uestion for research. The determination of sex is 

 certainly the more im[)ortant item, and possibly for this reason the 

 reduction ^ may be looked upon as following naturally in its train. 



But, [)erhaps, the two are inséparable; and indivisible; and, 

 therefore, it may be futile to inquire into the exact nature of their 

 mutual relationshi|)S. 



VIII. The Detenniiuitiori of Sex, 



The tracing-back wards of the sex in the end)ryo to earlier and 

 earlier periods has long occui)ied the attention of the writer. 'J'wo 

 years ago or thereabouts it had been followed (for the embryo — not 

 for the next generation) with greater or less certainty to the primitive 

 germ-cell, from which the primary germ-cells take their origin. But 

 the fact, that in the develoi)m(;nt of Jlaja batis there must be two 

 .sorts of eggs, producing .012 and 250 primary gc.'rm-cells resjjectively, 

 was the starting point for the present in(|uiry. The like fa,ct w(;iglied 

 heavily in the scale in leading to the conclusion, that the oogonia, 

 or their last division, or the oocytes, were concerned in the deter- 

 mination of sex for the following generation. 



The obvious interpretation of the two numbers was, that tlu; 

 smaller lelated to eggs, which at some earlier period had under- 

 gone an additional mitosis. For the lack of one division in the early 

 development, wh(;re the products in the two cases were of the like; 

 sizes, naturally meant, that it must have been carried out at some 

 I)revious epoch. It was irrational to suppose, that the missing division 

 had taken place among the early cleavage ones prior to the formation 

 of the primitive germ-cell. Therefore, it must have ha,pp(!ned in tiie 

 oogonia. This is as much as saying, that before the final division, 

 giving rise to the female oocytes, there was an additional one in thi; 

 forerunners of the male oocytes, as diagrammatically depicted in 



1) To prevent misconception it may be noted, that, notwithstanding 

 anything to the contrary in the earlier pages of this writing, the author 

 does not for a moment maintain the view, that the reduction of 

 chromosomes is ever effected \)y cell-division. 



49* 



