OF INSECTS. 14? 



selves into the canal in front of the chylifying por- 

 tion of it. In support of the older and more geiie- 

 rally received opinion, that the function of these 

 ressels is analogous to that of the liver, it is alleged, 

 hat by their insertion in the intestinal canal they 

 correspond to the gall-secreting organs of other 

 mimals; that there is often a bladder-shaped dis- 

 ention where they join the canal, forming a kind of 

 jail-bladder; that the vena porta which conducts 

 he blood to the liver takes its rise from the fatty 

 natter within the ventral cavity, as is the case with 

 he vessels in question ; and that the liver of closely 

 tllied animals (such as crabs, and annelides) consists 

 ike wise of such vascular appendages to the intes- 

 ine.* Amid these conflicting sentiments, a mixed 

 opinion best harmonises with the facts, and such 

 las accordingly been adopted by Meckel, Tiedemann, 

 F. Mliller, and Burmeister; viz. that the vessels in 

 [uestion have a double function, sometimes secret- 

 ng bile, at other times urine. Whether they secrete 

 he one or the other probably depends on the point 

 >f their opening into the canal being within the 

 egion of the chylific ventricle, or posterior to it. 

 n these circumstances, the name suggested by M. 

 ^udouin might be advantageously substituted for 

 .he present, for the most accurate knowledge we 

 low possess of the functions of these vessels thus 

 )roves them to be urino-biliary. 



The changes which the alimentary substances 

 mdergo in the part of the canal behind the insertion 

 )f the vessels just spoken of, depends in some 

 * Burmeister 'B Manual, p. 371. 



