HETEROCHROMOSOMES IN MOSQUITOES. 115 



During the summer only acetocarmine preparations were used 

 and the material resembled Culex so closely that only a few 

 figures were made. Other figures were taken from sections of 

 ovaries and testes fixed in Flemming and stained with thionin. 

 An oogonial prophase is shown in Fig. 23, and the chromosomes 

 from three spermatogonia in Figs. 24, 25 and 26. Fig. 27 is the 

 nucleus of a spermatogonium in prophase. In no one of these 

 figures is there any indication of inequality in the members of 

 any pair of chromosomes. Neither in resting spermatogonia 

 nor in the growth stages of the spermatocytes could anything 

 resembling the heterochromosomes of Anopheles be found. In 

 all of these stages a central plasmosome is surrounded by a 

 spireme as in Culex. Figs. 28 to 30 show a contraction or synizesis 

 stage, and two later growth stages. As in Culex the plasmosome 

 stains a deeper blue in late growth stages than in the spermato- 

 gonia and synizesis stages. Fig. 31 is a characteristic prophase 

 of the first spermatocyte mitosis. In the metaphase two of the 

 chromosme pairs nearly always appear in the form of rings and 

 separate as V's; the third pair is usually separated and its uni- 

 valent components already divided longitudinally, when the 

 rings are just dividing (Fig. 32). The second spermatocyte 

 propha'ses (Figs. 33 and 34), metaphases and anaphases resemble 

 closely those of Culex. 



The testes of Theobaldia differed from those of Culex in having 

 much larger spermatogonia and in lacking a prolonged prophase 

 of the first spermatocyte mitosis. The first maturation division 

 also shows characteristic differences in the behavior of the 

 chromosome pairs in metakinesis (compare Figs. 19 and 32). 

 Otherwise both ovaries and testes showed similar conditions in 

 the two species, Culex pipiens and Theobaldia incidens; i. e., 

 three equal pairs of chromosomes, no one of which behaves in 

 any respect like the heterochromosomes of other insects, including 

 Anopheles punctipennis. 



Anopheles sp.? 



On March 30 and again on May 31, a few pupae were obtained 

 from the same pond where I obtained my material in 1909. 

 All of the males in these collections had six chromosomes in the 

 spermatocytes and a distinct heterochromosome in the growth 



