186 PROCEEDINGS OF THE ACADEMY OF [Feb., 



There remain certain studies upon the spermatogenesis of insects, 

 the most deserving of attention of which are those of McCknig and 

 Gross. Vom Rath's studies of Gryllotalpa (1892, 1895) omit all the 

 earliest stages of the growth period ; and while he takes the stand that 

 the maturation is postreductional, he grants the possibility of its being 

 prereductional. McClung (1900, 1902) holds the postreductional 

 viewpoint, reasoning particularly^ from the forms of the definitive 

 chromosomes; in the late prophases of the first spermatocyte the bi- 

 valent chromosomes vary much in shape, rods, rings, crosses, and appa- 

 rently intermediate conditions. There is more uniformity in the first 

 maturation spindle. These difTerences in form McClung interprets as 

 successive stages and, to put it concisely, he argues that the axial rela- 

 tions of a chromosome change, so that if the long axis were originally 

 from right to left, it subsequently changes into a line at right angles to 

 this. X-shaped chromosomes are thereby interpreted as intermediate 

 stages in this transformation. His figures of Acridid spermatocytes 

 are very similar to those I give in the present paper of Syrbula of the 

 same family of the Orthoptera; but McClung holds that an elongate 

 bivalent chromosome placed with its long axis parallel to the first 

 mitotic spindle undergoes an equational division, therefore that the 

 line of separation of its univalent components lies along its length. 

 From the assumption that the diverse forms of chromosomes of the 

 late prophase are successive morphological stages he argues this change 

 of axial relations; and that might be justified if this premise were 

 proven. But that it is not is shown by the evidence given by me ( 1901a, 

 1904) that certain chromosome pairs are characterized by certain forms 

 in the spermatogonia as well as in the spermatocytes; a point which 

 Baumgartner (1904) has recently corroborated and amplified.^ Against 

 this evidence McClung does not bring satisfactory proof that the 

 differences in form express steps in axial changes. McClung's work 

 appears to be very accurate, but I cannot follow him in this interpreta- 

 tion, and would ask the critical reader to compare his descriptions and 

 figures with those on the related object given in the present paper. To 

 prove his point he has to assume a complex axial metamorphosis, 

 which is wholly unnecessary on the basis of a prereduction. The same 

 criticism applies to the study of Gross (1904) on Syromastes, which is 



* In the paper just mentioned Baumgartner claims that Sutton discovered a 

 difference in size of the chromosomes, and states that he himself has "been fortu- 

 nate enough to find a difference in form." I think I was the discoverer of both 

 of these differences and expressed them distinctly for various forms, as Baum- 

 gartner will find stated in my papers of 1901 and 190-4. But he deserves credit 

 for distinguishing constant forms among chromosomes of the first spermatocytes. 



