IIO N. M. STEVENS. 



Anopheles punctipennis. 



Very clear oogonial plates were found in several ovaries, and 

 two of these are shown in Figs. I and 2. There are two equal 





<? 



5 6 



FIGS, i and 2. Anopheles punctipennis, chromosomes of the oogonia. Mag, 



'OO. 



FIGS. 3 and 4. Anopheles punctipinnis, chromosomes of the spermatogonia. 



me mag. 



FIG. 5. Culex pipiens, chromosomes of an oogonium. Same mag. 



FIG. 6. Culex pipiens, chromosomes of a spermatogonium. Same mag. 



pairs of chromosomes very similar to those found in other Diptera, 

 and a third pair which is clearly made up of a longer and a shorter 

 pair. Corresponding figures of spermatogonial plates are shown 

 in Figs. 3 and 4. Here the composite pair consists of a longer 

 equal pair, as in the oogonia, united with a smaller unequal pair, 

 the larger member of which is of the same relative size as the 

 members of the corresponding small pair in the oogonial plates. 

 All of the spermatogonial plates in this Anopheles material were 

 of this type. In Culex, on the other hand, no such inequality or 

 composite condition of one pair of chromosomes could be de- 

 tected. Figs. 5(9) and 6 (d 1 ) are new figures of the oogonial 

 and spermatogonial chromosomes of Culex pipiens, and those of 

 Culex tarsalis are of the same general character. 



