596 THE AMERICAN NATURALIST [Vol.L 



four rod-like pairs in place of two V-pairs. Next to type 

 A this type is of most frequent occurrence, being repre- 

 sented by six of the twenty-nine species. 



Spermatogonial figures have been examined in only one 

 of these species, D. virilis, and here no conspicuous in- 

 equality between X and Y is to be seen. One pair of 

 chromosomes appears to be larger in nearly all figures of 

 either sex, and a slight difference in length between the 

 two members of this pair may be seen in some male 

 figures, but it may be purely accidental. 



Type G 



Kepresented by 

 Drosophila funebris Fabr. New York, California, 

 North Dakota. (Metz, '14, Figs. 14-17, 8 Metz. 

 '16, Figs. 27-33.) 



This interesting type (type III of the previous paper) 

 is apparently a modification of type F, but differs from 

 it in the relative proportions of all of the chromosomes. 

 The m-chromosomes are so minute in most specimens as 

 scarcely to be visible, and for this reason were entirely 

 overlooked at first. Their conspicuousness doubtless 

 varies with the amount and kind of stain, and with the 

 fixative used, but even after making full allowance for 

 this there can be no doubt that the pair is much smaller 

 here than in most other species. Otherwise the type is 

 characterized by the smaller size of the short, rod-like 

 chromosomes and the greater length of the longest (sex 

 chromosome?) pair. As in the preceding case no con- 

 spicuously unequal XY pair is to be found in the males, 

 although a noticeable difference between the two large 

 chromosomes may be seen in some of the figures. 



Type H 



Represented by 



Cladochaeta nebulosa Coq. Cuba. (Figs. 15 and 

 16.) 



This species — the only known member of the genus — is 



s Fig. 14 (Metz, '14) and Fig. 27 (Metz, '16) are from the same cell; 



