62 bulletin: museum of comparative zoology. 



is evidence that the ordinary chromosomes have individual morpho- 

 logical characteristics. 



In striking contrast to the results of McClung and Sutton, Mont- 

 gomery ( :05) concluded that in Syrbula (an acridid) the first matura- 

 tion division instead of the second, is the reducing division. He 

 also found that the accessory chromosome of the spermatocyte is 

 represented in the spermatogonia by two chromosomes, and that it 

 divides during the maturation divisions in the same way as the other 

 chromosomes. Farmer and Moore (:05) also held that in the cock- 

 roach (Periplaneta) the first maturation division is the reducing divi- 

 sion. Moore and Robinson (:05) have reached the conclusion that 

 the so called accessory chromosome in Periplaneta is nothing more 

 than a true nucleolus, and that it disappears before the first matura- 

 tion division. On the other hand Stevens (:05'') has found that in 

 Blatella the accessory chromosome has practically the same history as 

 that described by McChmg, Sutton, and de Sinety for other Orthop- 

 tera. However, in Stenopelmatus (the California sand cricket) she 

 found a structure in the primary spermatocyte which, in position and 

 form, resembled the accessory chromosome, but differed from it in 

 mode of origin. During the first maturation division this element 

 passes bodily into one of the daughter cells, where it degenerates 

 before the second division. 



Some very surprising results have been reached by McClung (:05), 

 who believes that in several species of the Acrididae and in one locus- 

 tid (Anabrus) there is, even in the spermatogonia, a bivalent chromo- 

 some to the end of which the accessory chromosome becomes attached 

 during the prophase of the first spermatocyte division. In one species 

 the chromatic element formed by the union of a bivalent and the 

 accessory chromosomes unites with another bivalent chromosome 

 so that there is a single element composed of two tetrads and the 

 accessory chromosome. During the first maturation division one 

 entire tetrad and the accessory pass into one, the other tetrad into the 

 other daughter cell. 



Recently Otte (:06) has arrived at results diametrically opposed to 

 those of most of the preceding investigators. He finds that in the 

 spermatogonia of Locusta the chromosomes remain perfectly distinct 

 during the resting stage, each chromosome lying in a separate vesicle. 

 During the early growth stages of the primary spermatocytes the 

 chromosomes are in the form of chromatic filaments, which conjugate, 

 side by side, in pairs. The bivalent chromosomes thus formed are 

 divided transversely in both maturation divisions, there being no 



