WENRICH: SPERMATOGENESIS OF PHRYNOTETTIX MAGNUs. 103 
Of recent work on the Diptera, I may mention that of Stevens and 
of Taylor on Culex, and that of Metz on Drosophila. Stevens (’10a) 
finds parasynapsis in Culex, not merely in the growth-period of 
spermatogenesis, but among other kinds of cells. She says (’10a, 
p. 208):— “That parasynapsis occurs immediately after the last 
odgonial mitosis is certain and it is equally certain that the chromo- 
somes are similarly paired in earlier generations of the odgonia,” 
Again (p. 209):— “In Culex it is quite certain that parasynapsis 
occurs in each cell generation of the germ cells in the telophase,”’ and 
(p. 212), “It is interesting to find in Culex a clear case of parasynap- 
sis in odgonia, odcytes, spermatogonia, and spermatocyte prophases 
and then to see the same chromosome pairs appearing in the first 
maturation metakinesis as though united end-to-end.” (It is prob- 
able that she has overlooked stages in the postspireme showing the 
changes undergone by a parasynaptic spireme segment in its trans- 
formation into a metaphase tetrad). Miss Stevens found six to be 
the somatic number of chromosomes in Culex, the reduced number 
being three. The side-by-side pairing of the chromosomes in nearly 
all generations of cells studied, gave the appearance of a reduced 
number in many situations where it would not have been suspected. 
Taylor (’14) states that she found in Culex pipiens only three chromo- 
somes in all the stages that she studied, 7. e. in both the somatic and 
germ-cells of both sexes. This is a very surprising result, but an 
explanation may perhaps be found in the conditions observed by Miss 
Stevens, namely, the tendency for the chromosomes in all kinds of 
cells to pair between mitoses. A poor fixation might easily prevent 
one from recognizing the double nature of a closely adhering pair 
of chromosomes. Besides, Miss Taylor found some cells with six 
chromosomes, and shows figures of some others with more than three. 
It would seem more reasonable, then, to regard the prevalence of the 
reduced number found by Miss Taylor as the result of the constantly 
recurring tendency of the chromosomes to unite side-by-side between 
successive mitoses, and possibly to poor fixation. 
The results of Metz (’14) on Drosophila are interesting in this 
connection, for he reports conditions in these flies similar to those 
found in the mosquito. In this he confirms the earlier results of 
Stevens (’08). He finds (p. 55) that: — “The chromosomes not only 
exhibit a close association in pairs at nearly all times, but that before 
every cell division the members of each pair become so intimately 
united that they may be said actually to conjugate. Each pair, with 
the possible exception of the sex chromosomes, goes through what 
