Spertnatogenesis 503 



anaphase of the first spermatocyte, and sometimes to the meta- 

 phase of the second spermatocyte (Figs. 56 and 149) its individ- 

 uahty is marked. It takes the basic stains when the rest of the 

 chromatin takes acid stains; it frequently has a smooth round con- 

 tour in the early prophase, when the other chromosomes are irreg- 

 ular rods or tetrads; it usually is closely applied to the nuclear mem- 

 brane until that is dissolved, and then keeps an eccentric position in 

 the first spermatocyte equatorial plate; it does not divide in this divi- 

 sion, and either precedes or follows the other chromosomes to the 

 pole. In Vanduzea arcuata (Fig. 56), where it is intermediate in 

 size, and in Chlorotettrix (Fig. 149), where it is the smallest chro- 

 mosome, its individuality is still marked in the second spermato- 

 cyte. Finally the facts that have brought about the dropping of 

 the old discussion about prereduction and postreduction, speak 

 for the individuality of the chromosomes, in that they show the 

 essential point of reduction to be the separation of each maternal 

 chromosome from its paternal mate, and their distribution to differ- 

 ent spermatozoa. The uselessness of insisting on prereduction or 

 postreduction is shown within the order Hemiptera, where the odd 

 chromosome may divide in either division; in the Heteroptera, 

 it usually divides in the first, while in the Homoptera, the usual 

 place of division is the second spermatocyte, but Archimerus and 

 Banassa are exceptions in the former and Enchenopa in the latter. 



Value of the Number of Chromosomes in Taxonomy and Evolution 



McClung ('05) states that for Orthoptera, a certain number of 

 chromosomes is characteristic for each family, the chromosome 

 grouping marking the genus, and the relative size of the chromo- 

 somes indicating the species. Unfortunately this is not true for 

 the Hemiptera Homoptera as the number varies within the family 

 and even within the genus, being constant for the species only. 

 The case of Aphrophora quadrangularis may make this doubtful, 

 although it seems more probable that two or three species have 

 previously been included under one name, than that in the same 

 species, the reduced number should be sometimes 12 and some- 

 times II, which would not accord with the simplest laws of 

 heredity. 



