INSECTS. 255 



The intestinal canal of Insects is connected to the other parts 

 of the body partly by a large quantity of fat (the adipose body, of 

 which below), and partly by numerous branches of air-tubes, and 

 so retained in its place. 



In very many Insects Salivary Glands are present; they are 

 placed at the commencement of the intestinal canal. In Coleoptera, 

 for the most part, they are wanting; RAMDOHR found them in 

 Curculio ( GryptorJiynchus] lapathi, LEON DuFOUR, besides in other 

 Curculwnida, also in Blaps, Diaperis, Mordella and some other 

 Coleoptera; moreover in the other orders of Insects they are 

 present in by far the greater number of Families, probably in all 

 Orthoptera, Hymenoptera, Lepidoptera, Diptera and Myriapoda. 

 Amongst the Neuroptera they are wanting in Libellula and Ephe- 

 mera, amongst the Hemiptera in Aphides. It is very remarkable, 

 and not easily explicable, that in Panorpa amongst the Neuroptera 

 the female has no salivary glands, or more correctly only small 

 rudiments of them, whilst the male has them largely developed 1 . 

 They have here the form of long convoluted canals (three on each 

 side), which towards the end are turned upwards, and becoming 

 thinner terminate by blind extremities. This form of blind con- 

 voluted canals occurs also in the salivary glands of some other 

 insects, ex. gr. of the Lepidoptera; but it is by no means general, 

 for in the Hymenoptera and Orthoptera these organs appear commonly 

 as blind sacs grouped in clusters. Microscopic investigation has 

 demonstrated in these salivary vessels and glands, as in other 

 glands, a layer of epithelial cells with nuclei 2 . 



Below the inferior orifice of the stomach in Insects very fine 

 vessels are implanted, the so-called Malpighian vessels, which in 

 former times were generally looked upon as organs for the prepara- 

 tion of bile (vasa hepatica] an opinion still maintained by LriON 

 DUFOUR, OwEN 3 and other writers. It is, on the other hand, the 



1 Our meritorious countryman BRANTS first made this interesting observation, 

 Tijdsckr. voor not. Gesch. en Physiol. vi. 1839, bl. *73 T 9^- It was afterwards also 

 made known by LEON DUFOUR (Memoires presents a I' A cad. royale des Sc. vn. 1841, 

 PP- 582, 583, PL n, fig. 169,) who overlooked, however, the rudimentary salivary 

 glands in the female. 



2 See the beautiful investigations of H. MECKEL, MUELLER'S Archiv. 1846, s. 25 35. 



3 [It is not to be inferred that OWEN holds this opinion now : his Lectures were 

 published many years ago, and a new edition of them is now in the press.] 



