THE CHROMOSOMES OF PSEUDOCOCCUS NIPJE. 265 



to opposite poles. Its presence does however prevent haphazard 

 distribution in that the five chromosomes carrying this sex chro- 

 mation tend to remain clustered or grouped and therefore go to 

 the same pole. 



Although more or less contrary to the cytological evidence 

 furnished by other groups of insects, it may not be amiss to sug- 

 gest the possibility that in animals with haploid males each 

 chromosome carries a certain amount of sex chromatin. It 

 follows that the diploid female would then represent 2 X, whereas 

 the haploid male would represent I X. In the haploid male the 

 reduction division is not truly abortional as has been supposed, 

 but is merely a division in which these sex chromatin carrying 

 chromosomes go to one pole while the opposite pole receives no 

 chromosomes simply because the mates to these chromosomes are 

 absent. It is of interest to note that the straggling or lagging so 

 often observed in the sex chromosomes of various insects is 

 paralleled by the scattered and irregular distribution of the chro- 

 mosomes on the spindle of this division in the Hymenoptera. And 

 lastly, such irregular distribution is found also in the reduction 

 division of Pseudococciis niptr. 



Pseudococciis nipcc thus would stand half way between forms 

 with haploid males where every chromosome carries sex chro- 

 matin, and forms in which the sex chromatin is carried in very 

 few chromosomes and there is little numerical variation in the 

 chromosomes of the two sexes. In other words, half of the 

 chromosomes in the males carry sex chromatin. 



Although superficially an instance of Weismann's postulated 

 ideal type of reduction in which the diploid number of chromo- 

 somes is halved without previous syndesis, the spermatogenesis 

 of Pseudococciis nipcc nevertheless follows the commonly ac- 

 cepted lines of meiosis. The apparently exceptional behavior 

 can be explained as due to an extreme mode of sex chromatin 

 distribution and is not a unique example of the Prim&rtypus of 

 reduction. It may be remembered that Goldschmidt ('05 and 

 '08) gave this name to an instance of Weismann's simple type 

 which he thought to have discovered in Zodgonus minis. The 

 Schreiners ('08) examining Goldschmidts slides believed to have 



