1NSKCTA. 



967 



Fig. 424. 



Alimentary canal'of Carabus mortilia. 



h, oesophagus ; i, gizzard, or proventriculus ; b, 

 ventriculus or digestive stomach ; I, ilium ; m n, 

 colon, with caecal glands ; o, rectum ; p, hepatic 

 vessels ; q, their point of insertion , a, anal ves- 

 sels ; a, b, c, a gastric vessel j a, b, a portion of the 

 lining of the gizzard. 



examined by transmitted light, there is a slight 

 appearance of circular fibres. Its texture 

 throughout is distinctly muscular, both longitu- 

 dinal and transverse muscular fibres being dis- 

 tinctly visible in every part of it, and of nearly 

 uniform size. This is a remarkably low form 

 of development in an insect which afterwards 

 becomes one of the most perfectly organized of 



its class. The next kwnple form of afamentary 

 canal occurs in the ame order of insects, as in 

 the larva of the common Hornet, Vespa crabro, 

 in which it consists of a straight and gradually 

 enlarging tube, extended as far backwards as 

 the eleventh segment, where it becomes con- 

 stricted, and forms a short small intestine, 

 receiving at the same time the insertions of 

 very minute hepatic vessels, after which the 

 intestine becomes again slightly enlarged to 

 form a rudimentary colon. The next somewhat 

 more developed form is found in the Apnl(e, as 

 in Anthophoru retusa, in which the canal forms 

 a distinct oesophagus, which terminates in a very 

 slight dilatation, and then gradually enlarging, 

 passes onwards, as in the Hornet, until it ac- 

 quires its largest diameter in the eleventh seg- 

 ment, and becomes constricted to form the 

 small intestine, receiving laterally at the same 

 time the insertions of the hepatic vessels. The 

 small intestine then passes forwards, and after 

 making one short sigmoid turn backwards, ends 

 in a straight colon and anal aperture, which is 

 distinctly developed in this insect towards the 

 latter part of the larva period, at which time, 

 after the insect has become full grown and 

 ceased to feed, we have observed faeces passed 

 from it, but we have reason to believe that the 

 anal aperture is not developed until that period, 

 since no faeces are found in the cell in which 

 the larva is inclosed until after the larva is full- 

 grown, and has eaten the whole of the food that 

 was stored up with it when the cell was closed 

 by the parent. In the larva of some Coleop- 

 tera, as in the Lamellicorne*, there is almost as 

 simple a form of the alimentary canal as in the 

 Apidtf. In these, as in Melolontha vulgaris, 

 (jig. 425,) it commences in a short and narrow 

 oesophagus, which opens by a valve into a very 

 capacious stomach that extends backwards to 

 the twelfth segment of the body, where it is 

 gradually decreased in size, and ends in a nar- 

 rowed pylorus, which is divided internally by 

 a valve from a short and narrow intestine, 

 that passes forwards beneath the stomach, 

 and ends in a very large colon, which at its 

 commencement is dilated into an immense 

 ccecum, and is in general distended with faeces. 

 It terminates beneath the middle of the 

 posterior half of the stomach in a rectum, 

 which passes directly to an anal aperture. 

 In our dissection of this larva we did not observe 

 the exact point at which the biliary vessels enter, 

 but nevertheless they exist, although less distinct 

 than in the perfect insect. They were observed 

 by Swammerdam in the larva of Oryctes nasi- 

 cornis* entering, four in number, at the pylo- 

 rus. In this and other lamellicorn larvae the 

 surface of the digestive cavity is increased by 

 the addition of three series of ccecal appen- 

 dages. The first surround the cardiac extre- 

 mity, and consist of twelve ccecal tubes, with 

 their apices directed forwards, and dilated on 

 each side into four smaller creca, so that each 

 one has somewhat the appearance of a fern- 

 leaf. From the situation which they occupy, 

 these may perhaps be regarded as salivary 

 organs. A little beyond the insertion of these 



* Biblia Nat. tab.xxvii. fig. V. c. 



