172 THE COCKEOACH. 



The salivary receptacles are a pair of tliin- 

 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 duet, 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 theT^atter 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 loith 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 ' caeca are eight or seven csecal diver- 

 ticula of the anterior end of the mesenteron. 

 They are convoluted and club-shaped. 



Note the openings of the hepatic ccsca 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 inter- 

 laced among the tracheae and the filaments of the 

 fat-body all through the abdomen. 



0. The Respiratory System. 



The respiratory system consists of a series of tracheal tubes 

 containing air. These commence at the respiratory apertures, 



