ASSOCIATION OF CHROMOSOMES IN DIPTERA 237 



indicate the metaphase split; and figure 114 shows a corre- 

 sponding but somewhat later stage in the first maturation (re- 

 duction) division. 



Sciomyzidae 



Neurodena analis (figs. 115, 116). There is nothing peculiar 

 about the chromosomal behavior in the Sciomyzidae, so far as 

 I have been able to determine. Several specimens of N. analis 

 have been studied, with results comparable in every way to 

 those already described. The two accompanying figures are 

 sufficient to show the paired association and the relation be- 

 tween haploid (fig, 115, second spermatocyte) and diploid (fig. 

 116 spermatogonia!) groups. 



Trypetidae 



Flies of this family, so far as my experience goes, are not favor- 

 able for chromosome studies. Nevertheless they present suf- 

 ficiently clear figures to show that the paired association is present 

 here just as it is in other flies. Most of my studies were made up- 

 on Euaresta melanogaster, material of which I secured in Cuba. 

 The chromosome group of this species appears to be composed 

 of six pairs similar to those in the Muscidae, although no fig- 

 ures have been found that are complete and at the same time 

 clear enough to settle this point. 



Ortalidae 



No embryonic stages (larvae or pupae) have been secured 

 from any members of this family, and consequently no somatic 

 divisions have been studied. Spermatogonia! and spermatocyte 

 divisions have necessarily formed the basis of my observations 

 on both of the following species, yet there can scarcely be any 

 question that there is a definite correspondence between the 

 phenomena exhibited by spermatogonia and somatic cells. 



Chaetopsis fidvifrons (figs. 117-119). Chromosomal behavior 

 in spermatogonia of this species corresponds fully with that 

 described for ovarian and somatic cells in species of Drosophili- 



