I4O T. H. MONTGOMERY, JR. 



view ; in Figs. 25 only such chromosomes were drawn as could 

 be sent in their whole length ; and in none of the figures were 

 any chromosomes omitted that could be seen in their entirety. 

 Two chromosomes of a corresponding volume are marked with 

 the same letter, one in capitals and other in lower case, as, e. g., 

 A and a. All these cases were drawn, after numerous prelimi- 

 nary sketches, as accurately as possible with the camera lucida, 

 and then those which seemed to correspond were lettered alike. 

 Thus in Fig. I, the large chromosomes A and a are alike, but 

 differ in volume from all others ; B and b are markedly alike, 

 C and c, and all appear clearly paired. Sometimes, as in the case 

 of G, g, //, h, the two of a pair appear dissimilar in the drawings, 

 but this is simply because the curvature of one lies in a different 

 plane from that of the other. Thus in Fig. 3 are shown also 

 all 24 chromosomes, but the two marked x and y were seen so 

 obliquely that it could not be determined whether they were 

 alike. Fig. 6 shows a lateral view of a spermatogonic spindle, 

 showing also a similar pairing of some of the chromosomes ; and 

 Fig. 7 shows the same phenomenon in an oblique pole view of a 

 portion of one plate of daughter chromosomes of an early sper- 

 matogonic anaphase. 



An examination of these Figs. 1-7, shows that the chromo- 

 somes are paired according to their volumes, that the two of a 

 pair are very frequently of the same form ; and that in most 

 of the cases the two of a pair lie in the spindle close together. 

 The only interpretation for this last condition is that correspond- 

 ing chromosomes must have been arranged close together in the 

 continuous chromatin spirem of the prophase, so that in the 

 spirem A would be next to a, B to b, and so on. But on a 

 study of nuclei in the late prophase (loose spirem) stage, I was 

 not able to determine this positively, for until the chromosomes 

 have shortened to their definitive forms, they are so irregular 

 and twisted that it is practically impossible to determine their 

 exact lengths on sections ; probably crush preparations (such as 

 those employed by Sutton) could be used with advantage here. 

 At least there is no doubt of a continuous linin spirem in the 

 spermatogonic prophase and of the arrangement of the chromo- 

 somes in a chain along this thread. And it is probable that 



