256 CLASS viii. 



opinion of most writers of the present day, that they correspond to 

 the kidneys of the higher animals, whence the term used above 

 p. 254, (vasa urinaria) for these vessels. Besides other grounds for 

 this opinion, it is supported by chemical investigation 1 . These 

 vessels appear to be present in all Insects, with the exception of 

 Aphidii amongst the Hemiptera, where it has not been possible to 

 find a trace of them. Their number is very different, and seems 

 to be on the whole inversely proportional to their length ; they are 

 short and very numerous, more than twenty, in the Hymenoptera and 

 Orthoptera, and in Libellula and Ephemera amongst the Neuroptera. 

 Here they are arranged in a ring round the intestinal canal which 

 they perforate, whilst at the free extremity they terminate coecally. 

 In Gry llotalpa and AchetaY ABE. they fall into a common canal before 

 opening into the intestine. In the remaining Insects there are 

 usually only four or two of them present (Diptera, Hemiptera, 

 many Coleoptera), or six, as in other Coleoptera (the Heteromerata, 

 Tetramerata, and Trimerata). When there are only two, they 

 form a loop on each side of the intestinal canal, which seems to 

 arise from the fusion of two vessels ; and so open by four termi- 

 nations into the canal. In those Coleoptera which have six, they 

 are also attached to the inferior extremity of the intestinal canal 

 (the Rectum) , but do not open into it there ; they run upwards as 

 very fine vessels between the coats of the intestine and terminate 

 blindly 2 . 



If we consider these organs as Kidneys it becomes uncertain 

 whether Insects have a Liver ; for the idea that these vessels may 

 represent at once both Kidneys and Liver (whence it has been 

 proposed to name them vasa urino-biliaria] is not, as appears to 

 me, the result of comparative investigation either anatomical or 



1 See RENGGER'S Physiologische Untersuchungen uber die thierische Haushaltung der 

 Insecten, Tubingen, 1817, 8vo. Comp. WUR/ER, Ckemische UntersucJiung des Sloffes, 

 ivelcher sick in den sogenannten Gallengefdssen des Schmetterlings der Seidenrausse 

 befindet in MECKEL'S Archiv. iv. 1818, s. 213 215. Also CHEVREUL found in the 

 matter of these vessels potass, ammonia and uric acid; see STRAUS Considerations 

 generates sur V Anatomic des Anim. articules, auxquelles on a joint I'Anat. descriptive du 

 Melolontha vulgaris. Paris, 1828, 4to, p. 251. In a Lucanus little stones have been 

 found in these canals consisting of uric acid. AUDOUIN Ann. des Sc. not. 2e Se*r. 

 Tom. v. 1836, p. 129. C. VERLOREN found in larvae of Lepidoptera (Sphinx ligustri) 

 no uric acid in these vessels, but hippuric acid, as he informed me by letter in 1843. 



2 LiDON DUFOUR, Mem. sur les vaisseaux biliaires des Insectes. Ann. des Sc. nat. 

 ae SeYie, Tom. xix. 1843, PP- 145182, PI. 69. 



