INSKriA. 



975 



/ 132. 



a, part of the hepatic vessel of the larva of Sphinx 

 ligustri when nearly full grown, showing the 

 " -i , /. |>art of the same in the pupa, the circa 

 disappearing. 



I >nrckheim, and others. From each of these 

 luppowd CU'CU in the larva of sphinx we have 

 traced an exceedingly minute anil transparent 



\hich bat appeared to be connected with 

 other delicate ramifications, and sometimes 

 with llii! immense quantity of adipose sacculi 

 with which the whole viscera are siirroundeil. 

 These Malpighiau vessels undergo considerable 

 changes while the insect is passing from the 

 larva to ihe perfect state. The cocca begin to 

 disappear >oofl after the insect has entered the 

 pupa stale (//), and not a trace of them is dis- 



iile in i he perfect insect, so that the 

 function of the organ is gradually diminished 

 in activity. Durinu the larva state they exhibit 

 a remarkable peculiarity at their connexion with 

 the alimentary canal which seems to have some 

 ni< nun to their function. It is a dilatation 

 at the point of union of these vessels in the 

 sphinx to form a single duct that opens into 

 the ilium, and if these be hepatic vessels may 

 represent a gall-bladder, as once observed to 

 us liy Dr. (irant, but the exact function of the 

 vt ssels is very difficult to determine. The 

 following observation winch we made in the 

 summer of 1832 and have since repeated seems 

 a little to show the nature of the contents of 

 these vesst Is, and also of other parts of the 

 alimentary canal. \Ve gave sugared water, 

 coloured with indigo, to some specimens of 

 I'l/m-wi; mile,, which had been confined for 

 seven! hours without food after they had left 

 the pupa state. On t v. mining the insects 

 aUmt two hours afterwards the stomach was 

 found filled with fluid containing a great quan- 

 tity of pink-coloured granules, which appeared 

 to l)e the vegetable mdiL'o acted upon by the 

 acid contents of the stomach by which it had 

 In i 'oine salinatetl, thus distinctly indicating the 

 presence of an acid in the stomach during 

 diiii stion. Hut it was remarkable that some of 

 the indiuo that had passed the pyloric extremity 

 of the stomach, where these supposed biliary 



It filter, and had also passed throughout 

 the whole length of the ilium and even in pint 

 into the colon, had been restored again to 

 its original tlark blue colour, thus indicating 

 the piesence of an alkalescent fluid secreted 

 either 1>\ the hepatic vessels or the ilium along 

 which the mdi^o had passed. But another 

 curious circumstance .is that the hepatic ves- 

 sels also paitook of the same pinkish hue a* 

 the contents of the stomach, w Inch seemed to 

 indicate that the contents of these also are acid. 



The conclusions we drew from these observa- 

 tions, which we re|M-.ited \ery carefully in 

 mre, that there is an acid gastric juice 

 secreted in the stomach during diuestion, that 

 the contents of the so-called hepatic vessels are 

 probably also acid, and that an alkaline fluid 

 is secreted by the ilium, otherwise- the indigo 

 reddened in the stomach could not have been 

 uial colour. These circum- 

 stances seem to lead to the conclusion that tin- 

 Malpighiaii vessels are rather tinmfcrons than 

 biliary, more cs|>ecially as they have been 

 found by Chevreul* and Audoumf to contain 

 uric acid; but if this be really their function, 

 a question then arises why they are inserted so 

 near to the pyloric extremity of the stomach in 

 almost all insects, and the excreted fluid be 

 thus required to traverse nearly one-half of the 

 wholi- alimentary canal before it is ejected fiom 

 the body ? This consideration still inclines us 

 to sus[*:iid our opinion as to their true function, 

 and leads us still to believe that they may be 

 in some way connected with the function of 

 digestion and assimilation. 



The anal or proper uriniftrous urgara. We 

 agree with Bunneister that the anal arc tin- 

 true urinary organs. They do not in gent nil 

 evacuate their contents directly into the canal, 

 but on each side of the anus. They exist, a< 

 we have seen, in the Curabulf (Jig. 424, t), 

 and their general form, as long ago shown by 

 Uufour in these insects, is that of a long vessel 

 convoluted upon the colon and emptying itself 

 into an oval or kidney-shaped vesicle on each 

 side of the colon, and terminating in a single 

 duct close to the anus. Dufour found the 

 minute vessel on the colon connected with an 

 aggregation of rounded glandular bodies, each 

 connected with the vessels by a very minute 

 filament, but we have overlooked this structure 

 in our own examinations. Neither have we 

 seen it in the Dyticida, in which each urini- 

 fetous organ commences in two apparently 

 cu-cal tubes, which, after being a little convo- 

 luted, unite into one which empties itself into 

 a vesicle on each side of the colon and rectum. 

 Similar vesicles have been shown by Dufour in 

 the Stapliylinida, as in Stap/iyliium crythropteriu 

 and in the Silphida, in both which we have 

 ourselves distinctly seen them arising by a 

 single vessel which empties itself into an urinary 

 bladder on each side of the anus. In the 

 Uil/i/ii<l<e this bladder opens directly into the 

 term ination of the rectum. 



The adipose tissue. This tissue, which it is 

 necessary to allude to in connexion with the 

 organs of nutrition, consuls of an immense 

 number of little transparent membranous vesicles 

 filled with opaque adi|X)3c matter, which, in 

 the generality of insects, is perfectly white, but 

 in others, as in the butterflies, is of a bright 

 yellow colour. The vesicles are usually very 

 irregular in form, being sometimes nearly oval 

 and at others elongated or triangular. They 

 communicate freely with each other and form 

 a most intricate web or reticulated structure. 

 They cover the whole of the alKlommal viscera 



* Straus Duickhrim,Con9iJcral. &c. 1828, iv. 251. 

 t I/Iustitut. 135. 



