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PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXVIII. 



intestine appear circular in outline. But as development progresses 

 and the reproductive organs mature, they gradually encroach upon the 

 digestive tube and compress it. The ovaries or testes being located 

 above the anterior part of the stomach, push the latter together side- 

 wise and also push it downward, the result being that it assumes the 



Fig. 19. — Transverse section of Lepeophtheirus in the region of the second maxillipeds. 

 (After A. Scott.) b. s., blood spaces; c, chitin exoskeleton; m, muscle; mxp., maxillipeds; 

 n, ventral nerves; o, ovary; o. d., oviduct; s, stomach. 



form of a triangular prism, with one of the angles toward the dorsal 

 surface (fig. 19). 



In the genital segment, on the contrary, the convolutions of the ovi- 

 duct are below and outside of the intestine, and consequently push it 

 together sidewise and upward. The result is again a triangular prism, 

 but this time one of the angles points downward and a flat side is in 

 contact with the dorsal surface (fig. 20). By the time the sexual 

 organs are fully mature there has been a strong compression of the 

 digestive organs. 



Fig. 20. — Cross section of the genital segment of a Lepeophtheirus. (After A. Scott.) 

 b. s., blood space; c. g., cement gland; i, intestine; m, muscles; n, nerves; od., oviduct; 

 ov., ova. 



The wall of the digestive canal is not smooth, but is constricted trans- 

 versely at fairly regular intervals. When examined in the living 

 animal this wall is seldom at rest, but shows a series of peristaltic 

 movements passing intermittent^ along from the stomach to the 

 intestine, or vice versa. The action usually continues in the same 





