266 WM. REES B. ROBERTSON 



chromosome, in any cell of the body, and not only for the cells 

 of an individual or a species but even in the different species of 

 a genus and in different genera and subfamilies (though they 

 may have suffered considerable modification), is evidence to my 

 mind that in these structures we are dealing with at least genet- 

 ically continuous bodies. The same may be said in regard 

 to the V-compound chromosomes of Chorthippus. Here we 

 evidently have six pairs of rod chromosomes, so linking as to 

 form three pairs of V's which may be recognized individually 

 in all cells; for spermatogonia in the diploid relation; for first 

 spermatocytes in the pairing relation in all stages of synapsis 

 from stage 'i' on "to and through the metaphases, and (in dis- 

 junction) in the anaphases; and again in the haploid relation 

 in the second spermatocytes and spermatids. This habit of 

 association or linking in the case of these six particular pairs of 

 autosomes is the individually continuous relation which is 

 surprising. In the majority of genera it does not occur, at 

 least not for all six of these pairs of autosomes, but here in a 

 number of species occurring widely distributed in both Europe 

 and America, which systematists have, upon the basis of simi- 

 larity in external body characters, grouped into a single genus, 

 this habit of association between members of these six particular 

 pairs is constant. This signifies to my mind that there must 

 be more than a genetic continuity; there must be an individual 

 continuity of each specific V-chromosome through the spireme 

 stage from cell division to cell division, for it does not seem 

 likely that the connecting substance in the achromatic bridge 

 between two particular rod chromosomes in the case of each V 

 would be dissolved in a telophase only to be formed again at 

 the next prophase. 



If the interlocking which I have figured and described (fig. 

 163) and the Schreiners ('06b, figs. 24, 25) have likewise 

 illustrated is to be taken into consideration, then we have again 

 very definite evidence not of genetic but of individual con- 

 tinuity through the stages of the first spermatocyte nucleus, 

 where most doubt prevails as to the persistence of the continuity 

 of the chromatin thread. 



