476 Alice M. Boring 



maternal homologue of the odd chromosome, and the small mem- 

 ber is the paternal mate which is lacking with the odd chromo- 

 some. In the Coleoptera, the reducing division comes first, the 

 equational second. In this order of insects there is substantial 

 proof of McClung's sex determination theory, as the oogonial 

 equatorial plates have been shown to have the large chromosome, 

 while the spermatogonial plates have the small one, and there is 

 the same difference between the somatic plates of the males and 

 females. The theoretical bearing of these facts will be discussed 

 later. 



Hejniptera 



The chromosomes in this group are so large and few in number 

 that they have attracted many workers, but in spite of this fact, 

 there have been greater discrepancies than in almost any other 

 group. Henking ('90) in working on Pyrrhocoris apterus, was 

 the first to notice that in one spermatocyte division, one chromo- 

 some does not divide, thus causing a dimorphism of spermatozoa. 

 He counted 24 chromosomes in the spermatogonia, and thought 

 that this odd chromosome had the same valence as the others. He 

 observed a large darkly-staining nucleolus in the growth period, 

 although he did not associate a chromatic nature with it, or con- 

 nect it with the odd chromosome of the spermatocyte mitoses. 

 He formulated no theory to account for the dimorphism of the 

 spermatozoa. 



Wilcox ('95) records that there are 12 spermatogonial chromo- 

 somes in Cicada tibicens, and 24 spheroidal bodies in the sperma- 

 tocytes, instead of a reduced number, results similar to those on 

 Caloptenus femur-rubrum. 



In Anasa tristis, Paulmier ('99) describes two small sperma- 

 togonial chromosomes, which form first the chromatin nucleolus 

 in the growth period, then a tetrad which divides in the first sperma- 

 tocyte division, and not in the second. Because this chromosome 

 is small and appears in only part of the spermatozoa, he regards 

 it as degenerating chromatin. Wilson ('05c), working over the 

 same field, finds that Paulmier has confused two bodies, inas- 

 much as the two small chromosomes form a tetrad and divide in 



