156 Edmund B. ffilson 



are united (/, s) the large idiochromosome (/) being separate. 

 (Additional figures in Figs. 7, 8.) 



Fig. 2, a-c (terminalis, No. 21), show the corresponding stages 

 in an individual of the 24-chromosome type, with two large super- 

 numeraries. Their identification in the spermatogonial group 

 is somewhat doubtful. (Additional figures in Fig. 10.) 



Fig. 2, d, e (terminalis No. 34), show a 25-chromosome type 

 with three large supernumeraries. The growth-period (/) is from 

 an individual of granulosus (No. 54) that is possibly of the 26- 

 chromosome type. (Additional figures in Fig. 12.) 



Fig. 2, g, h (femoratus No. 42), and z (granulosus, No. 60) 

 show the 26-chromosome type with four large supernumeraries. 

 (See Photo. 28, additional figures in Figs. 9, 10.) 



Fig. 2, jl (femoratus, No. 40), are from a very interesting indi- 

 vidual of the 26-chromosome type, with two large and two small 

 supernumeraries (additional figures in Figs. 9, 10). The sperma- 

 togonia of this individual (k) uniformly show 26 chromosomes, 

 including four very small ones (two m-chromosomes, two small 

 supernumeraries), but the large supernumeraries and the small 

 idiochromosomes are doubtful. No case was found in which all 

 of the six components of the chromosome-nucleolus could be seen; 

 / shows five of them, including the two small ones. 



B ADDITIONAL DESCRIPTIVE DETAILS 



I will now give a somewhat more detailed and critical account 

 of the facts. Taken as a whole, the series (including nearly 300 

 slides of serial sections) presents a profusion of evidence on many 

 cytological questions that could not be adequately described save 

 in a large monograph; but I will here limit the account mainly to 

 the numerical and topographical relations of the chromosomes. 

 The clearness of the preparations is such that nearly all the prin- 

 cipal phenomena might have been illustrated by photographs (of 

 which upwards of 200 have been prepared). Thirty of these 

 are reproduced in Plate I, less for the purpose of giving the 

 evidence in detail than of illustrating its character to those not 

 directly familiar with this material. 



