130 bulletin: museum of comparative zoology. 



pods; by Griffin ('99) and Linville (:00) for molluscs; by Francotte 

 ('97), Griffin ('99), and Tretjakoff (:04) for worms. 



The results of most recent investigators, especially in vertebrates 

 and arthropods, lend strong support to the view of Gregoire, that 

 prereduction will be found to be the common if not universal type. 

 Montgomery ( :05) has strongly criticised the results of those who have 

 described a postreduction and has shown that in many cases, at least, 

 they are capable of a different interpretation. McClung (:00, :02) 

 has described a postreduction in the Orthoptera (Acrididae and Locus- 

 tidae), but, as Montgomery points out, in order to prove his point 

 assumes a complicated series of changes to take place in the chromo- 

 somes during the late prophase. Apparently McClung has confused 

 the rod- and cross-shaped chromosomes and considers that the former 

 are always slightly later stages of the latter. Undoubtedly the cross- 

 shaped elements do, as I have already described, become converted 

 into rods during the late metaphase, but this is later than described 

 by McClung and it by no means follows that the rods of the earlier 

 stages are formed in this way. 



Figure 62 (Plate 4) clearly shows several chromosomes which, 

 previous to the formation of the equatorial plate, are arranged with 

 their long axes parallel to the spindle axis. There is no evidence that 

 at this early stage the chromosomes have begun to divide. Moreover, 

 the rod-shaped elements can be distinguished throughout the entire 

 prophase, as I have already described in detail. 



McClung also lays great stress on the evidence afforded by the ring- 

 shaped chromosomes, as the following quotation from him shows: 

 "Reference was made on an earlier page to the conclusive evidence 

 offered by the ring figures with regard to the character of the first 

 spermatocyte division. This, I think, cannot be disputed. The 

 rings, with the point of cross-division to which the threads are attached 

 indicated by a slight projection, come to lie in the equatorial plate. 

 With the contraction of the fibers the halves of the rings separate 

 more and more until, at the point of final separation, the resulting 

 figure differs in no marked degree from that of the rod type." Con- 

 trary to McClung, I believe the evidence suggests strongly that the 

 slight projection on the rings to which the spindle fibers are attached 

 is not the point of cross-division but the point where the arms of the 

 loops overlap. If the division of the rings is accomplished in the 

 manner described by McClung, it is impossible to account for the 

 crossed condition of the components at the point of separation, which 

 undoubtedly occurs during the division of the ring-shaped chromo- 



