ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 967 



described in detail. The modifications of these structures are described 

 in six forms. 



b. Chylific portion. — The wall of the chylific portion consists of 

 five layers : — (1) cuticle, (2) epithelium, (3) connective and follicular, 

 (4) muscular, (5) serous layer. The three former constitute what is 

 usually described as the mucosa, and form the numerous circular 

 folds which are so conspicuous both externally and internally. 



(1) The chitinous cuticle becomes thicker posteriorly, and is pene- 

 trated by fine pores at right angles to the subjaceut epithelial cells. 



(2) The epithelium consists of a single layer of ordinary cylindrical 

 cells. Between the folds of the mucosa, however, the histological 

 structure is exceedingly like that of an epithelial gland. (3) The 

 connective and follicular layer consists of a conuective feltwork of in- 

 tersecting fibres, the meshes of which contain follicles. These 

 follicles consist of ovoid or spherical masses of compacted nuclei. 

 (4) As to the muscular layers, the internal is this time circular, the 

 outer longitudinal. The whole chylific region unites the character- 

 istics of a secreting and of an absorbing organ. The folds of the 

 mucosa form true valvulee conuiventes ; while the presence of follicles 

 in the connective layer, and the existence of a porous cuticle recall 

 the characters of vertebrate intestines. The structure of the complex 

 pyloric valve is described. 



c. ITie intestine. — In the intestine the cuticle is relatively thick. 

 The well-developed epithelial cells are flattened, cubical, or almost 

 spherical, according to the regions. Tho connective layer is weakly 

 developed and has no follicles. The muscular layers are disposed as 

 in the oesophagus. The intestine is distinguished histologically into 

 five distinct portions, which are described in detail. The first region 

 exhibits eighteen folds, the second twelve, the third six; this is fol- 

 lowed by a smooth portion, and by the terminal sphincter. 



d. The Malpighian tubes are next briefly noted. They exhibited 

 no special peculiarities. 



e. The adipose body forms a continuous sheath round the intestine. 

 The cells frequently appear to be disposed in cylindrical packets. 

 The component cells are large, and contain large refringent nuclei. 

 They colour rapidly under the influence of osmic acid. The tissue 

 round the oesophagus is looser, and the cells are smaller and more 

 granular. 



Larva living without a head.* — M. Francois notes the curious 

 occurrence of a living larva of Lavipyris noctiluca, in which the head 

 and a large portion of the prothorax had been removed and replaced 

 by a chitinous scar. There was not the least trace of head or mouth, 

 the digestive tube was normal, the oesophagus recurrent anteriorly, 

 the cervical nervous system drawn slightly backwards. In the normal 

 insect the oesophageal ring is not in the small head, but in the pro- 

 thorax. M. Francois gives a full description of the decapitated 

 larva, noting how the accumulated store of reserve nutriment still 

 supplied the necessary capital for life. 



* Coniptes Rendus, ciii. (18S6) pp. 437-8. 



