608 ZOOLOGY SECT. 



and (3) longitudinal tergal muscles, best developed in the abdomen. 

 The various segments of the limbs are capable of being flexed or 

 extended on one another, as in the Crayfish, by the contractions of 

 special muscles. The wings are little used, the female Cockroach 

 being incapable of flight, and the male not a strong flier : accordingly 

 the wing muscles are not very strongly developed. 



Between the body-wall and the alimentary canal is a cavity 

 taking the place of the coelome, but in reality forming a specially 

 developed part of the blood- vascular system (hmmocoele). This is 

 bounded externally by an irregular wall, formed of a mass of poly- 

 gonal cells constituting the fat-body. 



Digestive system. The mouth opens into a buccal cavity or 

 pharynx, which receives the ducts of the salivary glands (Fig. 502, 



^ 



mx.flp 



FIG. 502. Semi-diagrammatic view of the internal organs of female Cockroach, dissected 

 from the left side. The heart is not represented, abd. 1 , abd. 5 , first and fifth abdominal seg- 

 ments ; abd. gang.*, sixth abdominal ganglion ; an. anus ; ant. antennary nerve ; brn. brain ; 

 cer. cercus ; ccec. caeca ; coll. colleterial glands ; cr. crop ; gizz. gizzard ; gon. gonapophyses ; 

 inf. gang, sub-oesophageal ganglion ; int. intestine ; Ib. pip. labial palp ; I. ov. left ovary ; 

 malp. Malpighian tubes ; mx. pip. maxillary palp. ; od, points to the external opening of the 

 median oviduct (vagina) ; ces. oesophagus ; opt. optic nerve ; rec. rectum ; r.ov. right ovary ; 

 sal. glA. salivary glands ; sal. rec. salivary receptacle (left) ; sal. du. salivary ducts, indicating 

 the point at which the median duct of the salivary glands unites with the median duct of 

 the salivary receptacles ; spir. stigmata ; st. 7, sternum of the seventh segment ; te. 10, 

 tergum of the tenth segment ; th 1 , th 2 , th*, first, second, and third segments of the thorax ; 

 thor. gang 1 , first thoracic ganglion. 



sal. gld.). Each gland is divided into two lobes, made up of 

 numerous ramifications. In close relation to each gland is an 

 elongated thin- walled sac the salivary receptacle (sal. rec.). The 

 duct given off from the salivary receptacle joins that of the opposite 

 side and the median duct thus formed is joined by a single duct 

 (sal. du.), formed by the union of the two ducts of the salivary 



