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E. N. PAVLOVSKY 



influence the size of the cells, have been observed in the rectal 

 'sac of either the young or the mature larvae. 



The greater part of the hind-gut is occupied by the rectal 

 sac, which is located between the main tracheal side-trunks 

 (Text-tig. 13, trl). The high epithelium of the rectal sac has 

 not the significance of rectal glands, which are present also in 

 the larvae of some insects witli hemimetabolous development 

 in the shape of longitudinal stripes of high cylindrical epithe- 

 Uum (for instance, the rectal glands of Orthoptera). 



Text-fig. 13. 



Transverse section through one of hind segments of abdomen 

 with pleural ai)i)endages (pl(i). Rectal sac (ip) between main 

 tracheal trunks (trl). bm, brain. Zeiss, ob. AA, oc. 0. 



The presence of a cylindrical epithelium in the rectal sac 

 of H . c a r a b o i d e s is simply explained by the fact that in 

 this instance the anatomical border between the parts of the 

 hind-gut, which can be defined by superficial inspection, does 

 not correspond to the histological border between the tissues 

 composing it. 



Analogous relations have been observed by me in the poison 

 glands of Hymenoptera: its reservoir is similarly well 

 differentiated, and histologically it is built of a wall which on 

 one side bears a decidedly glandular character, and on the other 

 of that flat epithelium peculiar to the duct of the acid gland 

 (Pavlovsky, 1912). 



Eespiratory Organs. 



Two main longitudinal tracheal trunks enter a common 

 spiracle chamber (atrium stigmatique. Text-fig. 16, at) situated 



