746 JOHN BEARD, 



With the exception of their products no other cells in the Metazoan 

 developmental cycle have received so much attention as the oocytes 

 and spermatocytes. From the published researches on oogenesis and 

 spermatogenesis it must be apparent, that there exists a much closer 

 association between the determination of sex and the reduction of 

 chromosomes than has been suggested in the preceding pages. In 

 these, following Rückert, Hacker, Weismann, Vom Rath, and others, 

 the latter phenomenon has been assumed to happen in the two final 

 divisions of the oocytes and spermatocytes. It now remains to be 

 seen what light the standpoint of Boveri, 0. Hertwig, Guignard, 

 Strasburger, Brauer, Moore, Meves, Farmer and others throws 

 upon the question. 



As unlimited space is not at the writer's disposition, one of these 

 observers may be allowed to speak for the rest. The one chosen 

 may be Boveri, his words certain passages from the article "Befruch- 

 tung" (in: Ergebn. Anat. Entw., V. 1, 1891, p. 453-^67): 



"In oogenesis and spermatogenesis in some cell-generation or 

 other there takes place a reduction of the number of chromosomes 

 to the half." 



"A priori there are very different modes conceivable, in which 

 the reduction in number of the chromosomes may be effected, and it 

 appears to be open to question, whether it may be carried out by an 

 act of division." 



The author goes on to show, that in general the numerical reduc- 

 tion in chromosomes comes about before the formation of the polar 

 bodies, and at the latest in the oocytes of the first generation. 

 In Ascaris it does not happen earlier than this period. '"The reduc- 

 tion in the number of chromosomes takes place [erfolgt] in the oo- 

 and spermatocytes of the first generation." 



How in these the reduced number is brought to pass neither 

 Boveri nor any succeeding worker has as yet been able to make out. 

 He remarks, that the critical point, at which observation is brought 

 to a standstill, is the nucleus of the oocyte or spermatocyte of the 

 first generation. According to him, it is not the reduced number in 

 the actual egg, or polar bodies, or spermatozoa, which requires ex- 

 planation, but this diminished number in the oocytes and spermato- 

 cytes of the first generation. 



At this juncture the writer would mention, that in the same year 

 (1891) in his already cited memoir (p. 54—58) Hartog urged several 

 objections to the necessary correctness and validity of current views 



