474 Alice M. Bon II g 



phism of the spermatozoa corresponds to the dimorphism of sex. 

 McClung considers that the longitudinal division always precedes 

 the reducing division, and thinks that this is important on account 

 of the failure of the second polar body to be extruded in parthe- 

 nogenetic eggs; but the work in the other groups of insects shows 

 that the reducmg division probably comes first as often as the 

 equational. 



Sutton's careful work ('oo, '02) on Brachystola magna offers 

 convincing evidence for the individuality of the chromosomes. 

 Each pair of spermatogonial chromosomes becomes enclosed in a 

 separate compartment of the nucleus, while the odd chromosome 

 i« in a vesicle shut completely off from the others. He suggests 

 the application of Montgomery's theory of the union of maternal 

 and paternal chromosomes in synapsis to Mendelian inherit- 

 ance. 



The observations of de Sinety ('01) on the odd chromosome in 

 one of the Acrididae and in several Phasmidae are entirely in accord 

 with those of McClung; this chromosome divides in only one sper- 

 matocyte division, producing dimorphic spermatozoa. In one of 

 the phasms, he finds a chromosome complex similar to that de- 

 scribed later by McClung ('05) for Hesperotettrix, where the odd 

 chromosome attaches itself to one end of a tetrad, forming a hexad 

 which divides along the transverse axis of the tetrad, thus sending 

 the odd chromosome and two chromatids of the tetrad to one cell, 

 and two to the other. Unfortunately de Sinety interprets both of 

 the spermatocyte divisions as longitudinal, but on this point he is 

 in the minority among the workers on Orthoptera. 



Baumgartner ('04), in Gryllus domesticus, finds the odd chromo- 

 some in a separate vesicle as Sutton did for Brachystola, but he 

 finds it dividing in the second division instead of the first. Stevens 

 ('05a) in Stenopelmatus and Blatella germanica, and Otte ('06), 

 in Locusta viridissima, find that the odd chromosome divides in 

 the second division instead of the first. Evidently there is no fixed 

 rule as to where the odd chromosome shall divide. 



Voinov ('03), Montgomery ('05) and Zweiger ('06) all hold a 

 different view as to the valence of the orthopteran odd chromo- 

 some; but as each has studied only one species of the order, while 



