110 INTERNAL ANATOMY OF INSECTS. 
some, screw-shaped l : in one larva, with hemispherical 
elevations 5 : in the cockchafer, part of them are fringed 
on each side with an infinity of short, blind, minute, 
setiform tubes, while the rest are naked c ; they are 
composed of a single, thin, transparent membrane, ac- 
cording to Ilamdohr' 1 ; but Cuvier thinks their texture 
is spongy . They appear to contain a number of small, 
irregular, dark granules, which float in a peculiar fluid, 
with which, however, they are not always filled through- 
out, nor are they constantly permeable from one end to 
the other. Thus in the meal-worm beetle {Tenchrio 
Molitor), the common trunk by which they arc attached 
to the intestinal canal is composed of gelatinous gra- 
nules f . The place of their insertion is generally a little 
below the pylorus, but in the common cockroach they 
are inserted into the stomach just above that part". 
Usually each vessel opens singly into the intestinal ca- 
nal, which the whole number surround at an equal di- 
stance from each other' 1 . Sometimes, however, they are 
connected with it by a common tube in which they all 
unite, as'in the asparagus-beetle {Lcma Asparagi' 1 ), and 
the mole-cricket [Gryllolalpa vulgaris k ) ; in the house- 
fly (Musca domestica), and other Muscidtr, each pair 
unites so as to form a single branch on each side of the 
canal previously to their insertion ' ; in the field-cricket 
(Grylltis campestris) they are all inserted in one spot" 1 ; 
a Notonccta glauca, Ibid. t. xxiii./. 5. 
b Of Musca vomitoria, Ih'ul. t. xix./I 5. 
c Ibid. t. viii./. 1. II. and G.f. 2. " Ibid. /iO. e Ibid. 
f Ibid. e Ibid. U.t. If. 9. b Ibid. '< Ibid. I. \).f. 5. II. 
k Kidd in Philos. Trans. 1825. t. x\.f. 6. 
• Ibid. t. xix./. 1. N, N, 0,f. 2. P, P, O. 
m Ibid.t. \.f. l.hkh. 
