50 TJie Larva of Chirononius 



beliind. There is no separate rectum, and tlie parts 

 known in other insects as crop and gizzard are not 

 distinguishable from the rest of the oesophagus. The 

 stomach, small intestine, and colon all begin at their 

 maximum width and gradually narrow behind. 



The usual appendages of the alimentary canal are the 

 salivary glands, the glandular caeca, and the Malpighian 

 tubules. All these are found in our larva. 



Nomencia- We shall devotc a few lines to the nomenclature of 

 *'^'^' the parts of the alimentary canal in insects generally, 



and to the definition of the terms which will be employed 

 here. The alimentary canal in all insects is divided on 

 developmental grounds into three primary sections : — 

 (i) the fore-gut or stomodaeum, Fr. preintestin, Ger. 

 Vorderd'arm ; (2) the rnid-gid or ivesenteron, Fr. medi- 

 intestin\ Ger. MiUeldarm ; (3) the hind-gut ov proctodaeum, 

 Fr. posfinfestm, Ger. Hiuterdann. The mid-gut is the 

 primitive alimentary canal, and in animals which pass 

 through a well-marked gastrula- stage, it is at first a large 

 internal cavity, formed by infolding of the hollow blasto- 

 sphere, and lined by entoderm (hypoblast). The fore-gut 

 and hind -gut arise by infolding of the ectoderm from 

 the mouth and anus respectively. In all Arthropods 

 they are lined by chitinous cuticle. The beginning of 

 the hind-gut is marked, in nearly all insects, by the 

 insertion of the Malpighian tubules '^. 



The fore-gut of insects includes the oesophagus, and 

 often exhibits a large dilatation, which may be followed 

 by a chamber with thickened muscular w^all and dense 

 chitinous lining. The lining may be shaped into internal 

 teeth or ridges. For the dilatation the name crop (Fr. 

 jabot, Ger. Kropf) is in general use, while the muscular 

 chamber is called gizzard (Fr. gesier, Ger. Kaiimagen). 

 Plateau'' objects that the so-called gizzard of insects 

 has no analogy with that of birds. This is put strongly ; 



* This term is proposed by Biilbiani, 1890, p. 3. 



^ Ptychoptera, according to Gehuchten, 1890, and Meloidae, according 

 to Beauregard, 1886, are exceptions. Here the Malpighian tubules are 

 said to pass off from the mid-gut. The same peculiarity is believed to 

 obtain in scorpions. 



' 1874, p. 114. 



