344 Procccdiiu/s of the Ohio State Academy of Science 



units of the species. And since it is known that paternal and ma- 

 ternal equivalents conjugate in the formation of the hivalent 

 chromosomes, it follows that no difference how the univalents 

 are segregated, each daughter nucleus will still have all the types 

 of true chromosomes and so the com])letc inheritance of the 

 race, including sexual tendencies. 



If one thinks of organisms as continuous develoi)ments 

 from generation to generation and each individual as a branch 

 from the main axis of progression, then sex in most cases be- 

 comes simply an individual expression of a more general inherit- 

 ance, in many cases even an alternative expression when female 

 determining cells give rise to males or vice versa. The alterna- 

 tive expression is then probably of the same nature as alterna- 

 tive expression in the formation of leaf and flower shoots in a 

 branching plant. 



SEX PKODUCIXG NUCLEAR BODIES. 



In a large number of insects belonging chiefly to the Hemp- 

 tera and Coleoptera a definite chromosomal diflFerence has been 

 found between the male and female. The "accessory chromo- 

 somes" or allosomes are so distributed at the time of the reduc- 

 tion division that all the eggs are alike while the sperms are of 

 two kinds. The chromosome group of one of the two types of 

 sperms is like that of the egg, and when such a spenn fertilizes 

 ^^ ^SS s female zygote is produced. The other type of sperm 

 has a chromosome group unlike that of the egg and produces a 

 male zygote in fertilization. An attempt has been made to find 

 similar peculiarities in plants but so far without success. I 

 shall touch but briefly on the presence of these sex-determining 

 bodies as discovered by McClung and worked out for many 

 species by Stevens. Wilson, Montgomery, Morgan, and others. 

 These "accessory chromosomes," "idiochromosomes," or allo- 

 somes as Montgomery calls them are said generally to arise from 

 or to be closely connected with a chromatin nucleolus. Now in 

 plants, at least in all cases where the objects are of such size 

 and distinctness as to warrant definite conclusions, the chromo- 

 somes come from the chromatin network. If then the alio- 



