I4O M. \V. lil.ACK.MAX. 



But other tests may be applied and have been applied. Baum- 

 gartner 1 (:O4), made an attempt to distinguish the chromosomes 

 in Gryllns by differences in form. He reaches the conclusion 

 that in Gryllns certain definite shapes constantly occur and estab- 

 lishes the probability that there is a fixed number of each type. 

 Davis 2 (:o8), working upon various Orthoptera reaches the con- 

 clusion that "In addition to the difference in volume, the bivalent 

 autosomes (chromosomes) show constant and characteristic dif- 

 ferences in form. In general several more or less distinct morpho- 

 logical types can be distinguished, and the members of each type 

 appear to bear a constant numerical relationship to each other." 



Robertson, :o8 (op. cit.}, does not consider the shape of the 

 chromosome of first importance in establishing its identity but 

 considers size as the primary characteristic, while shape is second- 

 ary and to a certain extent dependent upon size or at least upon 

 the degree of lengthening. The main criticism I wish to make 

 regarding Robertson's conclusions on this point is that in his 

 study of the chromosomes, he has not drawn them from the best 

 view point to establish any characteristic difference in shape. 

 His drawings are all or nearly all of chromosomes as seen in polar 

 view, whereas a view at right angles to the spindle is more satis- 

 factory in determining both the shape of the chromosomes and 

 their relation to the mantle fibers. 



In Scolopendra, as I have already implied, it is impossible to 

 establish the identity of many of the chromosomes on the basis of 

 size alone. Early in my work, however, after six or eight chromo- 

 some groups had been carefully drawn, it became evident that the 

 chromosomes as seen in a lateral view of the metaphase of the 

 first spermatocyte are of several distinct types as regards shape 

 and that the size relation of the chromosomes of each type are 

 such as to make it possible to distinguish the individual chromo- 

 somes with some degree of certainty. This, I think, will be 

 apparent from a Mudy of the figures of plates I. and II., although 

 it must be borne in mind that the figures are of course much less 

 satisfactory for this comparison than the actual chromosomes, 



"Baumgartner, \V. J., 104. "Some New Evidences for the Individuality of the 

 Chromosomes," BIOL. BTLL , Vol. 8, pp. 1-23, 3 plates. 



'Davis, H. S., :o8, "Spermatogenesis in Acridickc and Locustida?," Bull. Mm. 

 Comp. Zoo/. Harvard Coll., Vol. LIII., pp. 59-158, 9 plates. 



