DAVIS: SPERMATOGENESIS. 131 



somes, but to which McCkmg makes no reference. However, in 

 the forms upon which this author worked, it is difficuh to demonstrate 

 satisfactorily the sequence of the divisions, and I was myself for some 

 time imcertain on this point. But in Stenobothrus I believe there 

 can be little doubt that the arms of the large loops are separated during 

 the first mitosis. McClung himself has later (:05) described a pre- 

 reduction in certain chromosomes of various Orthoptera. In several 

 of the Acrididae and one Locustid the monosome becomes attached 

 to the end of a bivalent autosome during the prophase of the first 

 division, and in such cases the autosome divides reductionally during 

 the following division, although McClung still maintains that the 

 remaining autosomes divide equationally. It is significant that in 

 the autosome in which he finds a prereduction the free ends of the 

 univalent components are so clearly marked that there can be no 

 room for doubt on this point. In Mermiria this author finds that the 

 element formed by the fusion of the monosome and a bivalent auto- 

 some end to end later unites with another bivalent autosome and 

 that, "Upon the separation of the chromosomes in the metaphase the 

 multiple chromosome is divided so that to one pole there goes a triva- 

 lent eleuKMit and to the other a bivalent one, the difference in valence 

 being due to the presence of the accessory chromosome in one daughter 

 cell. There occurs here an entirely unique separation of chromosomes, 

 for by means of it entire tetrads pass into the second spermatocytes." 

 Such a division seems very improbable and requires much more con- 

 clusive proof than this author has been able to bring forward. A 

 comparison of his Figure 12 with Figure 91 (Plate 6) of the present 

 paper suggests that the "multiple chromosomes" of Mermiria may 

 be capable of a different interpretation. This seems more probable 

 when we remember that Mermiria and Stenobothrus are members 

 of the same sub-family, the Tryxalinae. At another place in the 

 same paper McClung refers to the unsymmetrical character of the 

 daughter elements derived from the division of the multiple chromo- 

 some as follows: "Among the uncertainties in my mind concerning 

 the behavior of the chromosomes in Mermiria, is one relating to the 

 nature of the association of the chromosome into the multiple element 

 of the first spermatoc^-te. The tetrads seem of the usual type, i. e. 

 have simple chromosomes of equal size, but when the dyad divides 

 it would appear as though there were some heterogeneity present, 

 for in the anaphase one limb of the loop is longer than the other. 

 This may be due to the formation of a multiple chromosome partly 

 from the accessory chromosome; otherwise it means that the tetrad 



