60 McCLUNG. 



words, have we not a right to suppose that their phylogeny is 

 paralleled by their ontogeny? If this be granted, then we have 

 at least more ground for belief in the individuality of the chromo- 

 somes than if we had never known of a time when they were of 

 necessity independent." 



56. Of interest in connection with the question of the general 

 distribution of the accessory chromosome are the observations of 

 Miss Wallace ('oo) upon the male germ cells of the spiders. The 

 general facts of the case are found in the following quotations 

 from her preliminary paper : " In this spider the peculiar chro- 

 mosome is conspicuous in the late spermatogonic stages, and in 

 the prophase of the first spermatocyte, its peripheral position in 

 the nucleus making it easy to observe. Its origin in the sper- 

 matogonia has not yet been traced, but a gradual change of form 

 has been made out in the early stages and, suffice it to say here, 

 that in all of them it appears to be double. 



57. " In the monaster of the first spermatocyte the accessory 

 chromosomes are easily distinguished from the others by their 

 sharpness of outline, slightly greater affinity for staining reagents 

 and above all by their eccentricity of position. They are always 

 found on the periphery of the spindle and often near the pe- 

 riphery of the cell. It is a curious fact that in the majority of 

 cases both of these elements are found nearer one pole than the 

 other." 



58. Regarding the unequal distribution of the accessory chro- 

 mosome to the spermatozoa, she is unable to speak definitely. 

 Her observations on this point are stated in the following words : 

 " In the spider the position of the two chromosomes nearer one 

 pole gives the impression that this unequal distribution occurs in 

 the first spermatocyte division. One thing, however, opposes 

 this interpretation and that is that in the monaster of the second 

 spermatocyte division two elements are again found in eccentric 

 position but of half the size of those found in the preceding cell- 

 division. The position nearer one pole might mean merely de- 

 layed distribution but there is not yet at hand sufficient data from 

 which to draw a conclusion." 



59. In the latest edition of his work upon the cell, Wilson ('oo) 

 takes cognizance of the investigations being pursued by insect 



