H. M. Morris 99 



with its inner surface, is a layer of flattened, irregular-sized cells. ATiall 

 and Hammond QT) consider that these are the "Wandering cells." In 

 this larva this snb-hypodermal layer of cells appears to be continuous. 

 The scales consist of a thin stratum of the outer layer of cuticle, which is 

 not continuous beneath them, the interior of the scale being occupied 

 by cuticle of the inner layer. The hypodermis does not enter the scales 

 although it bulges outwards slightly towards their bases. The processes 

 are of similar structure, the hypodermis bulging upwards barely to the 

 base. 



The Di^stive System. 



The alimentary canal takes a nearly straight course through the 

 body from the front of the head to the end of the last segment, but it is 

 slightly longer than the body. It is divided into Fore-Gut, Mesenteron 

 or Mid-Gut, and Hind-Gut, and is provided with salivary glands, caeca 

 and Malpighian tubes (Text-fig. 9, p. 113). 



The Fore-Gut extends from the mouth to the end of the first segment 

 of the body. 



The mouth is formed by the labrum above, the mandibles at the sides 

 and the labium and maxillae below. The inner surface of the labium 

 (the epipharynx) bears numerous short setae, the arrangement of which 

 is shown in Text-fig. 6, p. 112. Some of these setae are probably 

 sensory while others may assist in holding and cutting the food. 



The mandibles are mostly used in taking the food into the mouth, 

 and are moved in the same, or almost the same plane, but their shape 

 causes the food between them to be worked against the epipharvnx. 

 which bulges slightly downwards. Ju5t behind the mouth the fore-gut 

 dilates slightly into the pharynx, from the walls of which muscles radiate 

 to the walls of the head, and circular muscle fibres are present in its 

 walls. 



The Oesophagus (Text-fig. 9) is a straight and narrow tube of simple 

 structure. It is lined by a chitinous intima. which Is considerably 

 folded. Outside the intima. is an epithehum in which the nuclei can 

 be seen but not the cell walls. Outside the epithelium lies a muscular 

 coat, consisting of a layer of circular fibres, forming a series of transverse 

 rings. On the outside of the muscular coat is a thin membrane of c-on- 

 nective tissue. Towards the middle of the first segment of the bodv 

 the oesophagus dilates slightly, and the intima here becomes stronger 

 and has the appearance of small groups of teeth. Behind tbis is a short 

 region or Gizzard with very strongly developed circular muscles and of 



