THE INTEGUMENT. 37 



Lenticular Bodies of a highly refractive character are found 

 imbedded here and there in the endostracum, sometimes deeply, 

 more usually immediately under the epiostracum. These 

 bodies vary from -i mm. (-n-y^ of an inch) to mere granules. 

 They are very hard and brittle and consist of concentric 

 lamellae enclosing an internal cavity. Several are found near 

 the head. They apparently resemble the so-called calcareous 

 bodies of cestoid worms (Fig. 4, 6). 



The Hypoderm consists of large flat hexagonal cells, 70" to 

 80" in diameter, and 5O'- 1 or more in thickness. The nuclei of 

 these cells are distinctly vesicular, 40^ in diameter (see 

 ' Histology') ; some are cup-shaped next the cuticular layers, 

 and the cavity is filled by the rounded inner extremity of the 

 corresponding cuticular prism. Others are conical and fill 

 cavities in the cuticle below the projecting papillae on its 

 surface. Many send fine processes through the canals of the 

 endostracum (Fig. i, / and 2, /z). 



Basement Membrane. Several authors have described a thin 

 cuticular basement membrane beneath the hypoderm cells. 

 Such a membrane only exists just before the formation of the 

 pupa. 



Sub-hypodermal Cells (Fig. i, /, s and ./). Viallanes [27] first 

 described a fenestrated layer of cells beneath the hypodermis, 

 this is the connective tissue, or so-called peritoneal coat, which 

 is reflected from the surface of the internal organs over the 

 inner surface of the hypoderm ; it supports the tracheal net- 

 work. The individual cells are often stellate, and are con- 

 tinuous with the adenoid reticulum of the blood sinuses. 



3. THE HEAD AND MOUTH ARMATURE. 



The Head. The only portions of the head which can be 

 recognised externally are the maxillae, separated on their ventral 

 surface by the mouth, the prestomal and discal sclerites ; and 

 on their dorsal aspect by the epicranium. 



The Maxillae. The organs which I have so named form by 

 far the largest portion of the head, and each consists of two 

 parts separated by a slight circular sulcus a proximal and a 



