446 
Chas. W. iletz and Jose F. Nonidez 
The spermatocyte divisions. 
The matiiration divisions present no iinusual featiires, although tliey 
are much niore favorable for study than those of A. sericeus. The second 
division figures are almost diagrammatic. The cells are of ample size and 
the cliroinosomes stand out in hold relief, luaking it easy to exaniine them 
in detail. A typical fhst spermatocyte prophase is shown in fig. 29, in 
Avhich the seven chromosomes are readily distinguished. At this time 
the duality of the chromosomes is apt to be overlooked unless they are 
heavily extracted, but it becomes more noticeable as the metaphase plate 
is formed. 
Tetrads are not evident. 4Ve have found no indication of a secondary 
split preceding the first division in this species. Ordinarily the second 
division is forecasted only in anaphase, where the chromosomes spüt as 
they pass to the poles. A polar view of the first division is shown in fig. 30. 
Judging from the apparent absence of tetrads, this dinsion is reductional 
for all of the chromosomes, as it is for the sex-chromosomes. 
Interkinesis is relatively short, but is accompanied by a diffusion or 
intermingling of the chromosomes to form a sort of network, so that the 
individual members cannot be followed from one division to the next. 
Fig. 31 represents a metaphase and fig. 32 the two poles of an anaphase 
of the second division. 
Discussion. 
Discussion may be limited here mainly to those features which dis- 
tinguish the present case from that of Asilus sericeus discussed in our 
earlier paper (’21). As noted in that paper (p. 179) difficulties enter at 
once when we attempt to compare spermatogenesis in other families of 
flies with that in Asilus (Asilidae). In various species of Drosophila, for 
instance, most of the chromatin disappears from view very early in the 
growth period and usually does not reappear until the prophase of the first 
division. In other flies the chromosomes remain in view longer, but go 
through an extended diffuse stage in which they cannot be seen clearly. 
There are numerous differences in the superficial aspects of spermato- 
genesis in these cases, and it is not certain that they can be reduced to a 
common scheine. The only promise of doing this seems to be by means of 
studies beginning with the most simplified cases, such as those considered 
in the present paper. It is in this connection that Asilus notatus is of 
particular interest. Spermatogenesis in this form is sid’ficiently similar 
to that in A. sericeus to indicate that the growth stages are probably 
