64 PETER OKKELBERG 



as sex chromosomes may be plasmosomes and have nothing to 

 do with the determination of sex. Wilson ('13) found a body 

 in the spermatocytes of Pentatoma that sunulated an accessory 

 chromosome, and which he called a 'chromatoid body.' A similar 

 body has been found by Wodsedalek ('14) in the spermatocytes 

 of the horse and by Bachhuber ('16) in the spermatocytes of the 

 rabbit. More recently, Swingle ('17) describes what he consid- 

 ers to be the same kind of body in the spermatogonia of the frog 

 (Rana pipiens and R. catesbiana). The body was in all these 

 cases of cytoplasmic origin and was found with the chromosomes 

 only during mitotic division. 



An examination of the various figures given of a so-called sex 

 chromosome in vertebrates reveals a striking resemblance to plas- 

 mosomes similar to those that are found in the early oocyte of the 

 lamprey. Stevens ('11) describes such bodies in the spermato- 

 cytes of the guinea-pig; two such bodies were found by Wodse- 

 dalek in the spermatocyte of the pig; similar bodies were found 

 by Levy ('15) in the spermatocyte of the frog. Guyer ('09, '16) 

 has described such bodies in the spermatocytes, in the oocytes, 

 as well as in the body cells of the fowl, and ascribes to them a 

 sex-determining function. Finally, Jordan ('14) has found such 

 a body in the germ cells of various mammals. Bohring and 

 Pearl ('14) have studied the body found by Guyer in the domestic 

 fowl, and have come to the conclusion that it is not a sex 

 chromosome. 



At the present time the status of the sex chromosome in the 

 germ cells of vertebrates is very uncertain. It is unfortunate 

 that the subject has been studied almost exclusively in the male 

 germ cells. Von Winiwarter's account of such a body in the 

 oocyte of the cat and Guyer's description of the body in the female 

 germ cells of the fowl seem to be about the only accounts dealing 

 with the sex chromosomes in the female germ cells of vertebrates. 



It is generally assumed that when the spermatozoa in a species 

 are dimorphic, the female of the same species produces eggs only 

 of one kind. These correspond in their chromosome make-up 

 to the male cell possessing the sex chromosome. All the eggs, 

 therefore, in such species possess accessory chromosomes. On the 



