250 WM. REES B. ROBERTSON 



animal resulting from such a combination. At the formation 

 of zygotes, combinations must have been made having, for in- 

 stance, either an abnormally long no. 1, and a short no. 1 (figs- 

 136-140, 141-147) or two short no. I's (the most usual); and, 

 in the case of the no. 4's, one normal and one deficient no. 4, 

 or two normal no. 4's. While such a segmentation must be 

 uniform for every cell division in this animal as a result of Men- 

 delian segregation and recombination, the same chromosomes 

 in the next generation will have to give rise to an entirely differ- 

 ent segmented spireme at each division. This cannot be imagined. 

 The same may be said in respect to the V's and their rod-mates 

 in Jamaicana, where we have undoubted evidence of Mendehan 

 segregation and recombination, since in the same species there 

 were individuals having two pairs of rods, and again two rods 

 and one V, or in another species two V's. It seems to me that 

 it will have to be admitted by Meves, Duesberg, and others that 

 these abnormal chromosomes persist from one cell division to the 

 next. In order to do this they must remain independent of each 

 other and of the mates with which they pair, for pairing in this 

 case is proved to take place. They must be identical from cell 

 to cell of the same animal, for in the one-V type of Jamaicana 

 subguttata every cell, except one-half the second spermatocytes, 

 possessed this V-chromosome. The same may be said of any 

 of the other abnormal chromosomes. These chromosomes per- 

 sist as entities from one cell division to another and especially 

 from the pre-meiotic to the first spermatocyte division; other- 

 wise how can we explain the repeated appearance of such irregular- 

 ities in so exactly similar a manner in all dividing cells of the 

 animal in which they happen to be? 



3. Do they conjugate side by side {parasynapsis, parasyndesis) 

 or end to end {telosynapsis , metasyndesis) or in both ways? The 

 only evidence I have to offer that is of any force in answer to 

 this question is that afforded by the V-chromosome compounds 

 in Chorthippus. As has already been shown (pp. 232-234), they 

 give strong evidence in support of the parasynaptic method of 

 conjugation. 



