Spcrmatogenesis in Asilus notatus Wied., (Diptera). 
439 
that the coiifused or contraction stage does not involve any significant 
changes in the chroniosomes, and that in essentials the chroniosome 
behavior agrees with that in Ä. senceus. 
In the present acconnt especial emphasis is laid on the earliest growth 
stages because of their iinusnal clarity. They serve even better than those 
of A. sericeus to reveal the association of chroniosome in pairs (bivalents) 
as they come out of the final spermatogonial telophase, and they also 
show the gradiial lengthening mit of these bivalents, without any formation 
of leptotene thrcads, . as growth proceeds. 
Technique. 
FLEimiNG’s strong solution has been found niost satisfactory for 
fixation and has been used almost exclusively. Heidenhain’s iron haema- 
toxylin and saffranin have been used for chromatin stains, with or without 
Counter stains. A more detailed consideration of technique has been given 
in an carlier paper (Metz ’16, p. 219). All of the accompanying figures 
are from material fixed in Flemming and stained in iron haeniatoxylin. 
Topographical features. 
The testes in Asilus, like those of most other asilids, are a pair of 
long coiled tubes, each containing a large number of cclls. The distal end 
of the testis contains a clearly marked spermatogonial region with a central 
of giant nutritive cells as shown in text fig. 1 (A). Then comes a 
29 * 
core 
