198 WM, REES B. ROBERTSON 



the number characteristic of the family — six pairs and one 

 ( cf ) or two ( 9 ) sex chromosomes, the pairs being in three groups 

 according to size relations characteristic of the family. The sub- 

 family character is also shown by a sex chromosome that in size 

 is near to the smallest of the complex, by a marked inequality 

 between the two largest pairs, and by small cells. It has the 

 generic characters: nearly the extreme of inequality between 

 the two largest pairs and smallness of the sex chromosome. 

 These similarities serve to put incurvatus into the same family, 

 the same subfamily, and the same genus as granulatus. 



According to the systematic descriptions of the species one 

 would expect the chromosomes to be more nearly alike in these 

 two species than in any others. The measurements are not 

 sufficiently accurate to be of use in specific relations. Attention, 

 however, should be called to the differences between the chromo- 

 somes of the two species. 



The difference in length between the 5's and 6's of incurvatus 

 (22.50 to 27.15) is not quite as great as in granulatus (21.83 to 

 27.70). The gap between the 3's and 4's is only shghtly less, being 

 13.40 to 14.30 compared with 14.18 to 15.42. The same may 

 be said of the smallest pairs (I's and 2's). There is a wider gap 

 between the smallest and the intermediate groups than in granu- 

 latus (Tables VI, VII). The sex chromosomes is slightly smaller 

 (11.95 to 13.45). Finally the cytoplasm of the cells is consider- 

 ably more dense in the former. These differences might be 

 spoken of as specific. However, they cannot yet be said to be 

 satisfactorily established. 



The zygote number (2V) of chromosomes has been shown in 

 follicle-cell mitoses, no spermatogonial mitoses being available. 

 These mitoses show that numbers and size relations may be 

 readily followed even in somatic cells. 



According to Table VII, the length ratios of the autosomes 

 in incurvatus are nearer to the average rod-shaped chromosomes 

 of granulatus (Table V) than to the first spermatocyte chromo- 

 somes (Table VI). This is due to the fact that the chromosomes 

 in the first spermatocyte of incurvatus (figs. 61-64) are still 

 in the late prophase, not pulled out unequally as in granulatus 



