COCKROACH. 



329 



Skin. There is an external chitinous cuticle and a 

 subjacent cellular layer the epidermis or hypodermis 

 from which the cuticle is formed. The newly hatched 

 cockroaches are white, the adults are dark brown. 



Moulting, which involves a casting of the cuticle, of 

 the internal lining of the tracheae, etc., occurs some seven 

 times before the cockroach attains in its fifth year to 

 maturity. 



The muscles which move the appendages, and produce 

 the abdominal movements essential to respiration, are 

 markedly cross striped. They 

 are in many cases attached 

 to special tendons, which 

 arise as cuticular invagina- 

 tions, and are lost and re- 

 placed at each moult. 



Nervous system. A pair 

 of supra-oesophageal or cere- 

 bral ganglia lie united in the 

 head. As a brain they receive 

 impressions by antennary and 



FIG. 175* Leg of cockroach. 



Optic nerves. By means Of a c., Broad expanded coxa; tr., troch- 



nairpH rnmrni<?Qnrp Qiirrniinrl anter;/., femur; #., tibia; ta., six- 



' SUrrOUna- j i nte d tarsus with terminal claws 



ing the gullet, they are COn- and adhesive cushions. 



nected with a double ventral 



chain of ten ganglia. Of these, the first or sub-cesopha- 

 geal pair are large, and give off nerves to the mouth-parts, 

 etc. ; from each of the ganglia of the thorax and the 

 abdomen nerves are given off to adjacent parts. There 

 are three pairs of ganglia in the thorax, and six in the 

 abdomen, of which the last is the largest. From the 

 cesophageal commissures visceral nerves are given off to 

 the gullet, crop, and gizzard. Besides the large com- 

 pound eyes, there are other sensory structures some 

 of the setae on the skin, the maxillae (to some extent 

 organs of taste), the antennae (tactile and olfactory), the 

 anal cerci (tactile), and possibly the oval white patches 

 on the head. 



Alimentary system. (i) The fore-gut (stomodaeum) is 

 lined by a chitinous cuticle continuous with that of the outer 

 surface of the body. It includes (a) the buccal or mouth 



