CHROMOSOMES OF MOSQUITO 535 



In figure 61 all three tetrads are in metaphase condition. The 

 small one, b, is shown at two foci. 



Figure 62 is a late metaphase, and figure 63 a similar stage 

 from a slide which was much decolorized. The separate chro- 

 matids are here plainly seen. Tetrad c strongly suggests text 

 figure 6. 



Figure 64 shows an early anaphase in which the small tetrad 

 b has divided before the others. 



The spindle fiber, wherever it can be distinguished, is always 

 attached near the center of the dyads, consistent with the con- 

 dition in the spermatogonia. 



3. Later anaphases and telophases. When the dyads have 

 separated in anaphase and are approximately at the poles, they 

 split longitudinally, forming three pairs of V-shaped monads at 

 each pole. In a side view of the anaphase spindle the chromo- 

 somes are often difficult to separate and inconvenient to draw, 

 due to overlapping. 



In figure 65, an oblique view of an anaphase, the dyads have 

 already split into monads. The two poles of a slightly later 

 stage are shown from polar view in figure 66. Figure 67 shows 

 an optical section of a similar stage cutting through each arm 

 of the monad Vs. Such appearances are very characteristic of 

 this stage. 



Figure 68 is a slightly later stage when the chromosomes have 

 reached the poles. The sister monads are drawn closely to- 

 gether, especially in their middles. At a is shown the upper 

 pole; b is an optical cross section of the spindle fibers; and c 

 shows the lower pole. The chromosomes at c are becoming 

 somewhat vesicular at their ends. The sister monads tend to 

 unite at this stage, beginning at the middle and progressing 

 toward the ends. 



Figure 69 shows five optical sections along the polar axis of a 

 first spermatocyte telophase. The sister monads separated in 

 the anaphase seem to have reunited in the telophase. In figure 

 69 a is at a higher focus than b. The numbers about the circum- 

 ferences of a and b mean that the chromosomes opposite those 

 in a are continuous with those numbered correspondingly in b. 



