346 Proceedings of the Ohio State Acadeuiy of Science 



The allosome appears to be one of a number of external 

 and internal influences which accomplish sex determination, and 

 it is probable that this influence is brought about either directly 

 or indirectly by a stimulus on the hereditary apparatus, the re- 

 sult of the stimulus showing itself in large and small spores, 

 large and small gametes, or male and female individuals. 



But great caution must still be taken lest we be led away 

 b}^ this seemingly clear case of sex-producing bodies in the 

 gametes of insects and other animals. The difference may after 

 all be only a coincidence to the sex-determining factor, and this 

 really appears to be the case according to some recent investiga- 

 tions by Morgan. In the phylloxerans which are gall-insects of 

 the hickories, the fertilized eggs produce only females. This 

 results because only functional female-producing spermatozoa 

 are formed — ■ the male-producing sperms degenerating. The 

 females that result from the fertilized eggs produce subsequently 

 both males and females parthenogenetically. Without going 

 into the complicated history of the development of the various 

 generations in the life cycle a few prominent facts may be 

 pointed out. In the two species. Phylloxera fallax and P. cary- 

 aecaulis, male eggs and female eggs are determined as such be- 

 fore there is any loss of chromosomes. The total number of 

 chromosomes is present, yet one egg is large and the other small. 

 The preliminaries of sex-determination for both sexes go on in 

 the presence of all the chromosomes. The large eggs produce 

 females, the small males. The male animal itself is produced 

 only after the elimination of two of the chromosomes, but the 

 sexual female and the parthenogenetic female are both produced 

 in the presence of all the chromosomes. It is apparent that we 

 have here something like in the heterosporous plants. Sex is 

 determined before the reduction division and the two sizes of 

 eggs are significant when compared with microspores and mega- 

 spores. In Phylloxera caryaecaulis a large preponderance of 

 male producers are developed. When it is recalled that all the 

 descendants can be traced to a single egg fertilized by a "female- 

 producing" sperm the results are very significant. Either exter- 

 nal conditions determine the result or else there is a strong "pre- 



