1906.] 



The Internal Anatomy of Stomoxys. 



527 



connecting band as in Glossina. The thoracic ganglion is somewhat pear- 

 shaped, and is supported by the internal chitinous skeleton of the thorax, 

 from the surfaces of which arise the wing and leg muscles. Six pairs of 

 nerves arise from the thoracic ganglion and supply the thoracic muscles. 



The abdominal nerve trunk continues from the posterior part of the 

 ganglion running down in contact with the abdominal wall. It gives off 

 three fine branches which supply the abdominal muscles, and ends in the 

 third segment of the abdomen by dividing into three. Each of these branches 

 again divides to supply the generative organs, the outer two running to the 

 ovaries or testes and the middle one to the muscles of the ovipositor or penis. 



Circulatory System. 



This consists of the heart and its continuation, the thoracic aorta. The 

 heart is a tubular organ of the same type as in Glossina with chambers, ostia, 

 and alary muscles. The wall, too, is composed of similar giant cells. Though 

 several stained preparations were made it was impossible, owing to the fat- 

 body which obscured all detail, to count the chambers and cells in the heart 

 wall. They seemed, from a comparison of all the preparations, to be reduced 

 in proportion to the smaller number (four) of abdominal segments possessed 

 by Stomoxys. 



The dorsal aorta consists of paired cells, as in Glossina, and runs up on the 

 dorsal surface of the intestine to end on the. oesophagus in a similar mass of 

 cells. On the surface of the proventriculus, to which it is bound down, it 

 becomes expanded and flattened, narrowing again to its termination. 



Male Generative Organs. 



These are comparatively simple. The testes (fig. 2, T.) are a pair of 

 smooth, oval, orange-brown bodies with a shallow ecpiatorial constriction. 

 Their colour is due to a pigmented coat as in Glossina, but there is apparently 

 not the same tubular structure. 



From the lower end of each testis arises a very fine duct (T).), short and 

 straight, which runs down to join the duct of the opposite side as the upper 

 limbs of a Y. From this junction an exceedingly short length of common 

 duct (CD.) runs into the bulbous upper end of a tubular organ, which 

 would seem to function as a vesicula seminalis. 



This vesicula seminalis (V.S.) is a flexible tube, often lying with two 

 U-shaped bends in its course. At its upper part it is bulbous, gradually 

 narrowing below this to end as an ejaeulatory duct, which crosses the rectum 

 dorsally from left to right, to enter the penis in front of it.; it does not thus 



