290 PROCEEDINGS OF THE ACADEMY OF [May, 



the posterior oi- rectum, Ouly the middle intestine coucerus us iu 

 this paper. Its anterior portion is of slightly larger diameter than 

 the posterior (fig. 1). The lateral walls are perfectly sti-aight; 



Sph 



PostSpii 

 Rec 



Fig. l. — Oniscus asellus (male, 12 mm.) X 10.— (In this and follow- 

 ino- figures mm. refers to tlie length of the animal, measuring from the 

 anterior margin of the head of the segment to the end of the uropods. ) 

 Slio-htly diagrammatic drawing to show relation of the digestive organs. 

 Ant., Med., ^'ost., anterior, median and posterior portions of tlie "mid- 

 gut"'; 3Ius., muscular coat of intestine, shown only at extreme anterior 

 end of "mid-gut"; Tyi)h., typhlosole ; Ilej)., hepatopaucreas ; Tes., 

 testis; Eec.S., receptacle of sperm; Vas., vas deferens ; Sph., sphincter 

 muscle; Post Sph., post-sphincter; Bee, rectum. 



