532 CLARENCE E. McCLUNG 



this configuration is established, appears very definitely when the 

 chromosome complex of the different cell generations is studied. 



Conditions of the spermatogonia! metaphase are presented in 

 figures 44, 46, 47, 49, pi. 6. First it may be noted that the num- 

 ber of chromosomes present is twenty-two instead of the usual 

 twenty-three, and that, of these, two differ from the remainder 

 and from the usual spermatogonia! rods in being atelomitic V's, 

 with more or less unequal arms. Even a casual study of these 

 differential elements reveals their divergence in both size and 

 structure. One is distinctly larger, and, under favorable con- 

 ditions, it may clearly be seen that its shorter arm is irregular in 

 outline and more lightly staining. In these respects it conforms 

 to the behavior of the accessory chromosome in many Orthop- 

 tera. So characteristic are these appearances that there can be 

 no doubt whatever in the identification of this arm of the V chro- 

 mosome as the accessory. The V chromosome, then, is a mul- 

 tiple, a tetrad, consisting of the two rod-shaped chromatids of 

 the accessory chromosome joined to the two corresponding rods 

 of a euchromosome, just as in Hesperotettix. At the angle of 

 the V, where the fiber is attached and where the chromosomes 

 join, there is, not infrequently, a clear break in outline. The 

 compound nature of this V is clearly evident from these facts. 



Inspection of the smaller V reveals no such indications of 

 heterogeneity, and only in shape does it differ from the remain- 

 ing elements of the complex. Its position in the metaphase 

 plate is coimnonly near the multiple V. For convenience of 

 comparison several of these pairs of V's in different stages are 

 shown in figures 47 and 49. The number of chromosomes pres-, 

 ent in the complex is therefore found to be twenty free telomitic 

 rods of various lengths, two rod chromosomes joined at their 

 inner extremities forming a V and one other V-shaped chromo- 

 some — a total of twenty-three, the number characteristic of the 

 family. The internal morphological evidence of the complex in 

 this generation is sufficient proof to establish this conclusion. In 

 addition however we have two confirmatory lines of evidence 

 which are of great value, viz., the subsequent history of these 

 structures in spermatogenesis and the conditions of the female 



