THE ACCESSORY CHROMOSOME. 79 



sentative of the species. Adverse conditions, on the contrary, 

 cause the appearance of the male form which then shares with 

 the female the representation of its kind 



Again, some species are influenced by favorable external con- 

 ditions to such an extent as to cause, not the entire suppression 

 of the male form, but only its subordination in numbers. Fi- 

 nally, there are forms where the numerical proportion of the 

 sexes is preserved with only slight variation even under great 

 extremes in environment. The first case we would consider as 

 an example of a weak, the second as one of moderate, and the 

 last as one of strong, sex potentiality. 



Let it be granted, then, that the demand for sexual representa- 

 tion is not equally strong in all species. It follows that we may 

 expect to find corresponding variations in the method by which 

 sex is determined. Such forms as exhibit a ready response to 

 environmental conditions will certainly be more easily influenced 

 even at a late stage of development than would the more stable 

 forms at the beginning. 



On this account, an answer to the second question could not 

 be a simple one. It is very probable that, in certain species, sex 

 is determined at the time of fertilization and can not be altered by 

 any later influences. Conversely, it has been experimentally 

 proved that the proportion of sexes may be materially altered by 

 changed nutritive conditions operating upon larval forms, or may 

 possibly be changed several times in the same individuals. But 

 because Yung raised the proportion of females from a normal 

 one of about 56^ to the unusual one of 92^ in the sexually un- 

 stable tadpoles of the frog, it does not follow that in all forms 

 sex is such a variable factor. It is simply an evidence that sex 

 is not a fixed attribute of organisms and that in this particular 

 case it is extremely unsettled. By no means can it be taken as 

 an argument that sex may not be established in the act of fertili- 

 zation. 



In refuting this view, moreover, we are not forced to rely en- 

 tirely upon negative inferences. In the case of the honey-bee, 

 it has long been known that sex depends solely upon the matter 

 of fertilization. From the impregnated eggs come the females, 

 queens or workers as circumstances dictate ; from the unim- 



