268 WM. REES B, ROBERTSON 



animal, but likewise for those of another individual, a female 

 taken at the same time and from the same spot as the male. 

 Both chromosomes were probably handed down from preced- 

 ing generations. The behavior of this chromosome, it seems , 

 to me, argues for the persistence of individual continuity in the 

 chromatin thread from cell to cell. Otherwise, how could the 

 constancy of size be maintained, especially in the case of the de- 

 fective chromosome? 



These again are arguments opposed to the views of Haecker 

 ('11) and King ('08) that the differing sizes of the chromosomes 

 are due to unequal growth. If their theory be correct, why 

 these permanent abnormalities in size? 



It seems to me that these abnormal chromosomes are even 

 more conclusive arguments in favor of continuity than the be- 

 havior of the supernumerary chromosomes, for in the latter we 

 have more or less independent bodies in the cell — in the former, 

 abnormal bodies linked up in one case with a chromosome which 

 we can readily recognize in the cell. We also have the advan- 

 tage in Tettigidae that we may there recognize all of the chromo- 

 somes individually. 



Specificity of chromosomes is so closely bound up with' in- 

 dividuality and genetic continuity that it is not necessary to 

 discuss it at length. Montgomery has pointed out that specificity 

 of function is at least implied in the permanent size differences 

 in so far as amount of chromatin is concerned, a large chromo- 

 some having more with which to maintain a function than a small 

 chromosome. Another case of specificity of chromosomes is 

 shown in the tendency of one pair (no. 4's) to precede the other 

 autosomes in condensation, and also that of at least one member 

 of this pair to associate with the sex chromosome in the first 

 spermatocytes of Syrbula and Chorthippus (figs. 149, 150, 155, 

 163-165, 168-170, 171-174, 178-180). Another case that might 

 be cited is the occurrence of the V and its rod-mates in Jamaicana 

 unicolor (figs. 196-199) within the same cell. This might be 

 cited as exhibiting not only a difference from the rest of the 

 chromosomes in forming V's, but likewise a difference in speci- 



