DAVIS: SPERMATOGENESIS. 87 



flattened and where the narrow side is turned toward the observer, 

 as in a portion of the thread at the right in the figure, it appears 

 practically the same as at an earlier stage (cf. Fig. 38). Later (stage 

 e, Fig. 40) the chromatin granules are clearly in pairs and the spireme 

 ribbon has become still wider. However, when the ribbon is seen 

 edgewise it still appears to contain only a single row of granules. The 

 appearance of the spireme during this period lends little support to 

 the view that the double threads shown in Figure 40 are formed by 

 an approximation in pairs of the separate threads shown in Figure 38. 

 As in Dissosteira, occasionally two single threads can be seen lying 

 side by side for some distance, but such an arrangement appears to 

 be purely accidental. On the supposition that the double threads are 

 formed by the approximation of two single threads, it is impossible 

 to explain such stages as are shown in Figure 39, which are common 

 and are certainly intermediate between those of Figures 38 and 40. 

 The position of such spermatocytes in the follicle leaves no room for 

 doubt on this point. Furthermore, I have carefully counted the num- 

 ber of threads connected with the distal pole during stage d, before 

 there is any trace of the longitudinal split, and although it is impos- 

 sible to obtain an accurate count of the threads at this time, yet it 

 appears to be approximately the same as the number of autosomes in 

 the spermatogonia. In other words, the number of spireme loops is 

 approximately one-half the number of spermatogonia! autosomes. 

 If the double spireme is formed by a side-by- side conjugation of single 

 threads, there should be at this time as many loops as autosomes in 

 the spermatogonia. 



2. Monosome. 



The monosome during the growth period differs from the same 

 element in Dissosteira only in small and unimportant details. 



D. Chortophaga viridifasciata. 



1. Autosomes. 



The history of the growth period in this species presents no essen- 

 tial differences from that described for Dissosteira, except in the 'case 

 of stage b. During this stage the chromatin collects into much more 

 distinct and widely separated masses than in Dissosteira, so that the 

 true significance of this stage can here be followed to much better 

 advantage. Figures 41 and 42 (Plate 3) show two cells in this stage 

 cut at right angles to each other. The chromatin masses are here 



