INTERNAL ANATOMY OF -TNSECTS, 115 
nected with it above are no less than twenty-three ceca 
or blind appendages, of various forms and dimensions ; 
the last pair but one of which is very remarkable, being 
bent like a bow, and furnished externally with four short 
clavate processes*, It is probable that some of these or- 
gans are analogous to the bile-vessels of other insects, 
When the Creator in his wisdom fixed the limits of 
the various tribes of animals, he united them all into one 
harmonious system by means of certain intermediate 
forms, exhibiting characters taken some from those that 
were to precede, and others from those that were to fol- 
low them, and this not only in their exfernal structure, 
but likewise in their zutfernal organization; so that we are 
not to wonder if in the same individual we meet with 
organs that belong to two distinct tribes, or if, remaining 
nearly the same in their prima facie appearance, they be- 
gin to exercise new functions. An instance of this we 
have seen in the dorsal vessel of insects, which in the 
Arachnida, though not materially different in situation 
or general form, by the addition of a small apparatus of 
arteries and veins becomes the centre and fountain of a 
regular system of circulation®. From the circumstances 
here alluded to, physiologists have been led to entertain 
very different sentiments with regard to the structure of 
the alimentary organs of the Class we are now to enter 
upon, the Arachnida: what some regard as a real liver, 
others look upon as an epzploon or caul ; and what the last 
denominate Jzle-vessels are by some of the former consi- 
dered as appropriated to the secretion of chyle®. Yet 
* Tbid. f. 2, 3. 5. &e. » See above, p. I3—. 
© Treviranus and Ramdohr are of the former opinion; and Meckel, 
Cuvier, Marcel de Serres, and Leon du Four, of the latter. 
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