THE CHROMOSOMES OF PSEUDOCOCCUS NIPyE. 261 



Both the denser bodies as well as the threads continue pro- 

 gressive condensation, and the former reach their final form some 

 time ahead of the latter (Fig. 12). They are then somewhat 

 oblong in shape, and take the haematoxylin stain with great inten- 

 sity and there can be no doubt of their chromosomal nature. 

 Somewhat later the erstwhile threads have also assumed this 

 form, and there are then ten of these bodies or chromosomes, 

 identical in size and shape. Those first evolved continue to be- 

 tray a certain affinity for each other, and in the metaphase plate 

 constitute a central group around which the other five chromo- 

 somes become ranged in no definite order (Figs. 13 and 14). 

 Aside from this very characteristic grouping, the only difference 

 between the two sets of chromosomes that is apparent consists in 

 the rate at which they evolve or the stage which is the starting 

 point of their development. 



Throughout this development, there has been no trace of a 

 tetrad formation. The general features of the case indicate that 

 the split which was spoken of as occurring at one stage is nothing 

 more than preparation for the equation division or else something 

 of the nature of the " Querkerbe " observable in lower Crustacea. 



Division now occurs in ordinary manner and ten chromosomes 

 go to each pole (Figs. 15 to 17). The arrangement of chromo- 

 somes in the daughter cells is not absolutely certain, although fig. 

 1 6 indicates that there also the characteristic grouping is retained. 

 Figures like these are too rare to admit of any definite conclusion 

 however. At any rate, the time in which such an arrangement 

 persists must be very short, for the chromosomes are generally 

 found in a more or less irregular heap (Fig. 18). 



The division just described is undoubtedly equational in char- 

 acter. Following it there seems to be no intervening further 

 development in the chromosomes of the daughter cells. Instead, 

 they begin to scatter in a longitudinal direction. This process is 

 not entirely irregular however for it results in their separation 

 into two groups of five each (Figs. 1 8 to 22). It is a remarkable 

 feature that these two groups are each characterized by a distinct 

 and different arrangement of their component chromosomes. 

 The group going to one pole assumes the form of a V or a 



