PHYLUM ARTHROPODA 



577 



FIG. 458. Right salivaiy glands and salivary recep- 

 tacle of Cockroach. (After Miall and Denny.) 



du.\ formed by the union of the two ducts of the salivary glands ; 

 the common duct thus formed opens into the buccal cavity 



(Fig. 458). A chitinous fold 

 of the floor of the mouth 

 forms the lingua or tongue. 

 From the buccal cavity 

 there proceeds backwards 

 a narrow oesophagus (ces.), 

 which leads to an elongated 

 saccular dilatable sac the 

 crop (cr.). On this there 

 follows the proventriculus 

 or gizzard (gizz.) a pear- 

 shaped chamber with the 

 broad end directed for- 

 wards, its chitinous internal lining raised up into a number 

 of horny teeth. A narrow passage leads from this to the 

 chylific ventricle a wide tube with glandular walls; from its 

 anterior end are given off eight 

 tubular hepatic coeca (hep. coz^) 

 blind tubes somewhat narrower 

 than the chylific ventricle. The 

 point of junction of the chylific 

 ventricle with the intestine is 

 marked by the presence of very 

 numerous thread-like yellow ap- 

 pendages the Malpighian tubes 

 (inalp.) which are the renal 

 organs of the animal. The in- 

 testine (int.) terminates in a dilated 

 portion the rectum (ret.) the 

 walls of which are longitudinally 

 folded. Of the entire alimentary 

 canal only a small part the 

 chylific ventricle with the ap- 

 pended hepatic caeca, is of the 

 nature of a mesenteron, the region 

 in front being a stomodaaum, and 

 that behind a proctodaaum. 



The heart is an elongated 

 tube, closed behind, open in front, 

 running along the middle line of 

 the abdomen and thorax, imme- 

 diately beneath the terga. In- 

 ternally the tube is divided into a number of chambers ; its 

 walls are perforated by a series of pairs of valvular apertures or 

 ostia. Running from the wall of the heart to the terga are a 

 VOL. i P P 



FIG. 459. Portion of a trachea of a Cater- 

 pillar. B, C, D, branches ; a, cellular 

 layer ; b, nuclei. (From Gegeubaur.) 



