

1905.| Anatomy of the Tsetse-fly (Glossina palpalis). 547 
the ostia next in front of them; and so on with unfailing regularity all 
the length of the heart, each ostium being separated from the alary muscles 
next in front or behind by just two giant cells. In front of the first pair 
of ostia are found two cells of the usual size on each side, then a pair of 
slightly smaller cells, which pass on into the walls of the thoracic aorta. 
Thus the entire wall of the heart is built up of 23 pairs of giant cells, 
not counting the ten couples of smaller cells which compose the five pairs of 
ostia; to wit, four pairs to each of the five chambers, two additional pairs 
behind the fifth pair of alary muscles, and one pair anteriorly, making the 
transition to the thoracic aorta. In view of the fact that the thoracic vessel 
is itself to be considered as a modified anterior portion of the heart, it is 
interesting to find that its delicate wall contains very large, flattened nuclei, 
arranged in pairs, right and left. 
The alary muscles consist of delicate fibrils, arranged in an irregular fan- 
like manner, uniting into a stout muscle-fibre which is distinctly striated. 
ENTEBBE, UGANDA, 
July, 1905. 
VOL, LXXVi—BP. DE 
