48 



As pointed out by Cuenot,* there are two kinds of cells 

 present in the connective tissue which contain reserve 

 material. These are the " cellules de Leydig " and the 

 " cellules proteiques." The former contain glycogen, and 

 are present in great numbers, especially when the period 

 of ecdysis approaches. The latter are also present in 

 great abundance, and contain proteid material. 



The cutaneous glands are also embedded in the 

 dermis. The muscle fibres stretch across the dermis, and 

 are attached to the inner side of the basement membrane. 

 The muscles when dissected appear to be attached to the 

 exoskeleton, but an examination of sections reveals the 

 fact that they do not extend farther than the basement 

 membrane. 



The chitinous layer of the integument is situated 

 on the outer side of the epidermis, and consists of several 

 layers. Commencing from the outside, these are as 

 follows : — 



(1) The cuticle (Text fig. 8, a.) is an extremely thin 

 structureless layer covering the whole of the chitinous 

 exoskeleton. Its continuity is interrupted at intervals 

 where the ducts of the cutaneous glands open to the 

 exterior. From the cuticle there arise numerous small 

 papillae, which are only seen when examined under the 

 microscope. These must not be confused with the setae, 

 which are visible to the naked eye and which have an 

 entirely different structure (see below). 



(2) The pigmented layer (b.) is a moderately-thick 

 layer containing pigment. In the hard parts of the 

 exoskeleton this layer is calcified. It has a laminated 

 structure, and the numerous layers of which this portion 

 of the exoskeleton is composed are parallel to the surface. 



(3) The calcified layer (c.) is the broadest layer of all 



* Cuenot, L. " Etudes phvsiologiques sur les Crustaces Deca- 

 podes." Archives de Biologie, T. XIII, p. 245. 



