3. THE INTEGUMENT AND ASSOCIATED STRUCTURES 



39 



open on to the surface of the body (Fig. 27). The walls of the gland are formed 

 of large cells with basal nuclei. Their secretion has an extraordinary nature, 

 consisting of two components — a granular material and large oblong laminar 

 bodies like those which are often encountered in the solitary gland cells of the 

 epidermis. On the outside the gland is clad with a thin layer of muscle fibres 

 and a peritoneal epithelium. The duct of the gland is formed by a layer of 

 small cells, secreting a thicker or thinner cuticle which lines its lumen. The 

 external aperture of the gland is often well marked in animals examined 

 in toto. 



Fig. 27. Pyriform gland of Spirvbracliia grandis from the metameric region of the metasoma. 

 eg - gland cell ; cut - cuticle ; dgt - duct of the gland ; ep - epidermis ;fm - muscle fibres of the gland ; 

 fn - nerve layer of the epidermis; mc - layer of circular muscles; ml- layer of longitudinal muscles; 

 pgt - pore of the gland; se - granular secretion; sf- lamellar secretion. (After Ivanov, 1960a.) 



