

CHROMOSOME GROUPS IN GALGULUS OCULATUS. 3OI 



It yet remains to bring these two classes of spermatozoa into 

 relation with the spermatogonial and oogonial numbers. Unfor- 

 tunately but two spermatogonial metaphase figures are shown 

 with entire clearness. They agree in showing each thirty-five 

 chromosomes (Fig. i, D and ^). It may be thought that this 

 evidence is not sufficient to establish the number with certainty. 

 However, the number in these two cases is quite unmistakable, 

 and as will be shown, it is the number to be expected from the 

 numerical relations observed in the spermatocyte chromosomes 

 and in the female. The female number (oogonia or follicle cells) 

 is, without a doubt, thirty-eight (Fig. 1, A, B and C). The 

 analogy which exists between the numerical relations here and 

 in those forms with an odd chromosome, where the female 

 number is one more than the male, makes the evidence all the 

 more convincing that thirty-five is the male number in Galgulns. 

 It is evident from these facts that the reduced female group must 

 contain nineteen chromosomes ; and that accordingly females are 

 produced upon fertilization by the nineteen-chromosome class of 

 spermatozoa ; males upon fertilization by the sixteen-chromo- 

 some class. 



Egg 19 + spermatozoon 16 = 35 (<?) 

 Egg 19 + spermatozoon 19 = 38 (9) 



So far, I have not ventured a new name for these characteristic 

 chromosomes which make up the pentad group of the second 

 division. At present I shall simply refer to them as differential 

 chromosomes as Wilson, '06, has done in the case of the idio- 

 chromosomes. 



Between the spermatogonial and the first spermatocyte divi- 

 sions occurs a very prolonged growth period, during which the 

 cell diameter increases approximately five times. Throughout 

 this growth period, between synapsis and the formation of the 

 chromosomes preparatory to the first maturation division, persists 

 a large deeply staining body, more or less comparable in time of 

 appearance and behavior, to the chromosome nucleolus of those 

 forms in which it represents the odd chromosome or the idio- 

 chromosomes. I have not fully followed the history of this 



