210 KANSAS UNIVERSITY SCIENCE BULLETIN. 



there was every possibility of insect spermatologists coming to 

 an agreement with regard to the maturation processes. Indeed, 

 with the exception of Wilcox, who occupies a unique and 

 solitary position in the field, workers upon the subject are 

 committed to a belief in the occurrence of a cross and a longi- 

 tudinal division of the chromosomes in the spermatocyte mito- 

 ses. The sole difference of opinion relates to the sequence of 

 the divisions. We have now to consider in connection with 

 insects the remaining possibility in tetrad formation — that 

 of two longitudinal divisions — which finds an advocate in de 

 Sinety. 



Because of a thorough acquaintance with the forms upon 

 which this author has worked, I do not hesitate to say that he 

 is entirely mistaken with regard to the character of the second 

 spermatocyte division. I am convinced of this because of the 

 fact that in the early period of my work upon Orthopteran 

 spermatogenesis I was inclined to place just such an interpre- 

 tation upon the phenomena encountered in the spermatocytes 

 of the Acrididse as does de Sinety. I soon became convinced, 

 however, that I was proceeding upon a wrong assumption, and 

 abandoned it in favor of the one which more extended observa- 

 tion taught me is correct. I hope to demonstrate here the 

 ground for my plain statement that de Sinewy is in error upon 

 the question of a double longitudinal division of the chromatin 

 thread during the formation of the tetrads in insect sperma- 

 tocytes. 



It is fortunate that our author has properly appreciated the 

 value of the early prophase in the determination of the struc- 

 ture of the first spermatocyte chromosomes, for we are here 

 upon common ground, and need only compare like stages in 

 order to reach our conclusions. As will be recalled, the statement 

 is made elsewhere in this paper that the typical chromosome of 

 the first spermatocyte is an approximately straight rod, split 

 longitudinally, and again cleft in its middle by a second fissure 

 at right angles to the first. Such an element is represented in 

 figures 15ft, 17, D and E of my paper upon the Acrididye, and 

 in figures 7, 9, 11 and 38 of the present one. Although this is 

 extremely common, and, as the photomicrographs show, unde- 

 niably present, de Sinewy does not figure it at all. The nearest 

 approach to such a structure is found in figure 123c, where a 



