506 Alice M. Boring 



SUMMARY 



1 An odd chromosome is present in the spermatogenesis of 

 22 species of the Hemiptera Homoptera, as shown in each case by 

 some or all of the following facts : 



a The spermatogonia have an uneven number of chromosomes. 



h A dense body takes basic stains in the growth period. 



c One chromosome stands in an eccentric position in the 

 first spermatocyte equatorial plate. 



d In the metaphase of the first spermatocyte division, one 

 chromosome does not divide, and has half the valence of the others, 

 as shown by its spherical shape when the others are like dumb- 

 bells. 



e In anaphase of the first spermatocyte division, one chromo- 

 some at one pole behaves differently from the others, either pre- 

 ceding or lagging behind. 



/ Half of the equatorial plates of the second spermatocytes 

 contain the same number of chromosomes as those of the first 

 spermatocytes, but half contain one les5. 



g Half of the spermatids contain a condensed body, taking 

 basic stains, which is the odd chromosome. 



2 The odd chromosome shows certain variations in behavior, 

 either individual or specific. 



a In the anaphase of the division where it does not divide, in 

 some cells it may precede the other chromosomes to the poles, 

 while in others it lags behind them. 



This mdividual variation is a characteristic of certain species, 

 the three species of Ceresa and Vanduzea arcuata, while most of 

 the species studied have the odd chromosome always lagging be- 

 hind, and Phlepsius irrotatus has it always preceding the others. 



h In Enchenopa binotata, it divides in the first division, and 

 in the second division, where it does not divide, it neither precedes 

 nor lags behind the others. 



c The shape of the odd chromosome in the growth period 

 varies. It may be always spherical or ovoid with a smooth con- 

 tour, as in the Fulgoridae, Cercopidae, Jassidae, and some of the 

 Membracidae. It may be long and uneven in contour as in Van- 

 duzea arcuata and Enchenopa binotata. 



