78 bulletin: museum of comparative zoology.' 



differ greatly from the corresponding stages in the Acrididae. The 

 nuclei are more irregular in shape and the chromatic granules are 

 much more abundant and more evenly distributed. The monosome 

 occu])ies a separate vesicle having a complete membrane of its own. 

 It is even separated from the rest of the nucleus by a thin layer of 

 cytoplasm. The autosomes on the contrary are all enclosed in a com- 

 mon membrane not being located in separate vesicles as Otte (:06) 

 found in Locusta. The monosome usually appears as an almost 

 homogeneous mass, but when strongly decolorized it exhibits a well 

 defined granular structure as in the rest of the nucleus, except that 

 the granules are much more closely aggregated. The monosome has 

 apparently no constant position in the cell, but may occur at either pole. 



During the ]irophase (Fig. 16) the chromosomes appear as con- 

 torted rod-shaped bodies which later shorten and thicken. In favor- 

 ably situated nuclei the monosome can be distinctly seen in a separate 

 vesicle (Fig. 16). In the equatorial plate (Fig. L, p. 77, and Plate 2, 

 Fig. 18) there are twenty-nine chromosomes, which always lie in a 

 single plane. This species is remarkable for the ease with which the 

 chromosomes can be counted, as they are usually so well separated 

 that there is not the slightest difficulty in distinguishing the individual 

 elements. There are always three chromosomes much larger than 

 the others; two of these are V-shaped and form a symmetrical pair, 

 while the third, a long rod-shaped element is unpaired, being, of 

 course, the monosome. A comparison of Figures 16 and 18 shows 

 that this is undoubtedly the chromosome which is contained in a 

 separate vesicle during the prophase. Its relative size leaves no room 

 for doubt on this point. The remaining twenty-six chromosomes can 

 be readily grouped in pairs. 



Figure K (p. 77) is a polar view of the metaphase of an epithelial 

 cell from the vas deferens. There are probably twenty- nine chro- 

 mosomes as in the spermatogonia, but they are so closely crowded 

 that I cannot feel sure the count is correct. However, there can be 

 no doubt that in these cells, just as in the spermatogonia, there are 

 three chromosomes Avhich are much larger than the rest, two of them 

 forming a symmetrical pair, while the third is without a correspond- 

 ing mate and undoubtedly represents the monosome. 



