180 THE COCKROACH. 



The salivary receptacles are a pair of thin- 

 walled sacs, one on each side of the crop, between 

 the two glands of its side. 



The ducts of the receptacles run forwards 

 and unite beneath the nerve-cord at the hinder 

 end of the neck to form a median duct, which 

 runs forwards to open into the mouth, behind 

 the base of the lingua. 



The ducts of the salivary glands unite to form 



one duct on each side : the two ducts thus formed 



run forwards and unite beneath the nerve-cord 



in the hinder part of the neck to form a median 



duct : this runs forwards between the nerve-cord 



and the median duct of the receptacles, and opens 



into the latter at the anterior end of the neck. 



Having made out the anatomical relations of the salivary 



glands, receptacles, and ducts, remove the whole apparatus. 



Stain it with carmine; dehydrate, mount in balsam, and 



examine with the microscope. 



Nuclei are visible in the walls of the ducts, 

 and in the secretory cells of the glands. 



The chitinous lining of the ducts shows a 

 spiral thickening. 

 b. The * hepatic ' cseca are eight or seven ceecal diver- 

 ticula of the anterior end of the mesenteron. 

 They are convoluted and club-shaped. 

 Note the openings of the hepatic cceca into the mesenteron. 

 3. The excretory system consists of sixty or more 

 Malpighian tubules, which are fine filamentous 

 diverticula of the anterior end of the ileum, 

 arranged in six bundles. They are very long 

 and convoluted, and are interlaced among the 

 tracheae and the filaments of the fat-body all 

 through the abdomen. 



C. The Respiratory System. 



The respiratory system consists of a series of tracheal tubes 

 containing air. These commence at the respiratory apertures, 



