PETER OKKELBERG 



birds the problem has not yet been cleared up. Guyer thinks 

 he has evidence that the spermatozoa are dimorphic in this form, 

 while the inheritance of sex-hnked characters in birds points to 

 the egg as being dimorphic. In his last paper on the subject, 

 Guyer ('16) again emphasizes the fact of the presence of two 

 kinds of spermatozoa in the common fowl, but admits the pos- 

 sibihty of only one kind being functional. If it be admitted 

 that the eggs also are dimorphic, it would be difficult to explain 

 why two kinds of cells should be produced in both sexes of the 

 offspring. 



The assumption of a dimorphism of both spermatozoa and 

 ova of the same species has been made before. Castle ('03) 

 proposed a theory of this sort. Such a theory necessitates the 

 further assumption of selective fertiUzation, for which there is 

 apparently no direct evidence. 



In a recent paper by Stockard and Papanicolaou ('16), deahng 

 with the hereditary transmission of degeneracy and deformities 

 in alcohohzed guinea-pigs, a statement is made that the junior 

 author is in possession of data which indicates that the female 

 guinea-pig, as well as the male, shares in the determination of 

 sex, and that in this species both ova and spermatozoa may be 

 dimorphic. Previous to this, Papanicolaou published some of his 

 results in Science ('15), where he states that the sex of the guinea- 

 pig is determined, sometimes by two and sometimes by three 

 factors, depending upon whether or not the mother had previ- 

 ously given birth to young. The three factors are: 1) The sex 

 tendency of the father; 2) the sex tendency of the mother; 3) 

 the change of sex tendencies in the female from litter to fitter. 

 If these observations prove to be correct, the sex potency of the 

 fertifized egg is not determined by a sex chromosome, unless 

 there be a selective fertifization that is subject to variation ac- 

 cording to the physiological condition of the parent. 



An accessory chromosome has not been found in all forms 

 studied. This does not, however, exclude the possibility of its 

 being present, since it appears that it may often be united with 

 some other chromosome. This seems to be the case in Ascaris 

 megalocephala among invertebrates and Necturus maculosus 



