32 



THEOPHILUS S. PAINTER 



Table 1 gives in a condensed form the results of all workers on 

 mammalian spermatogenesis in which the sex-chromosome has 

 been figured and described. (This list is complete to date as far 

 as known to the author.) 



A glance at the table will show that both the origin and the 

 form of the sex-chromosome are variable. It is interesting to 

 note that in the guinea-pig, the rabbit, and, one author claims, 

 for man, the X-Y condition has been described, while in all the 



TABLE 1 



Homo sapiens 

 Homo sapiens 

 Homo sapiens 

 Homo sapiens 



Dog 



Cat, domestic 



Armadillo 



Opossum 



Guinea-pig 



Rabbit 



White rat 



House mouse. 

 Horse 



Pig 



Cattle 



BEHAVIOR OP SEX- 

 CHROMOSOME 



1st div. reduc. 

 1st div. reduc. 

 1st div. reduc. 

 2nd div. reduc. 

 1st div. reduc. 

 1st div. reduc. 



1st div. reduc. 



1st div. 

 1st div. 

 1st div. 

 1st div. 

 2nd div. 

 1st div. 

 1st div. 

 1st div. 



reduc. 

 reduc. 

 reduc. 

 reduc. 

 reduc. 

 reduc. 

 reduc. 

 reduc. 



Guyer, '10 



Montgomery, '12 



Winiwarter, '12 



Wieman, '17 



Malone, '18 



Winiwarter and 

 Sainmont 



Newman and Pat- 

 terson, '10 



Jordan, '11 



Stevens, '11 



Bachhuber,.'16 



Allen, '18 



Yocum, '17 



Wodsedalek, '14 



Wodsedalek, '13 



Wodsedalek, '20 



rest of the cases we have the X-0 type of sex-chromosome. It 

 should be added, however, that a great many investigators have 

 failed to find evidence for sex-chromosomes in many of these 

 mammals for which it is reported.® 



Unquestionably, the evidence for the existence of the X-0 type 

 of sex-chromosome is very complete in some cases, such as in 

 the rat (Allen) or cattle (Wodsedalek), but in many other cases 



' Mention is made only of the papers in which an accessory chromosome has 

 been described and figured. A complete review of the literature will be found 

 in Ethel Browne Harvey's paper in the Journal of Morphology, vol. 34, 1920. 



