32 THE EARLY STAGES OF TABANID^ 



walls. Sometimes it seems as if they are filled with a dark tough 

 substance, projecting in the shape of a papilla or of a granulated 

 string into the lumen of the peduncle. Eight of these pedunculate 

 bodies, as Graber calls them, were present in the larva examined, 

 arranged in four pairs, lying one behind the other, giving to the 

 vesicle the appearance of an internally segmented organ. The 

 bodies of the first two pairs are of about the same size, 30 ji in di- 

 ameter, the length of the peduncle 26 ix, its width at the tip 1.8 ix. 

 The bodies of the two following pairs immediately touching one 

 another are considerably smaller than the rest, their diameter being 

 only 20 /x. 



The compound nature of the organ appears more distinctly than in 

 the serial arrangement of the pedunculate bodies, in the repetition of 

 the covers in which they are enclosed. There are not four such covers 

 or secondary sacs, however, but only three, as the two posterior pairs 

 of pedunculate bodies are contained in a common envelope. The 

 first sac is formed by the capsule itself; that is, by its rounded (head) 

 end. The pedunculate bodies are observed hanging by their pedicel 

 from the slightly invaginated upper wall, and, like the following ones, 

 turned from the inside towards the outside in a somewhat oblique 

 direction. The space in which the bodies are found, however, is 

 separated also from the remaining lumen of the capsule, and, as far 

 as could be seen, by a transverse septum issuing from the side walls. 



The second pair of pedunculate bodies is, however, surrounded by 

 an independent sac entirely separated from the main capsule, the 

 fixation of the pedunculate bodies themselves at the inner upper wall 

 of the secondary vesicle being exactly the same as that in the first 

 capsule. This second sac, however, is not completely closed behind 

 the pedunculate bodies, but is forming here only a neck-like con- 

 traction, its walls otherwise being continued into the following sac. 



The third inner sac resembles the second one in all essentials, but 

 encloses, as already mentioned, two pairs of pedunculate bodies, 

 which again, in a manner analogous to that in the former cases, are 

 inserted into its walls. 



Probably the last two sacs are evaginations of the fundus of the 

 common capsule, fitted into one another like the sheaths of an onion. 

 In this way the first pair is surrounded by one envelope, the second 



