AMPHIPODA. 



497 



triculus ^with a cuticular lining thickened into two paired sets of 

 chitinous plates, and provided with lateral setose folds forming 

 a straining apparatus. The mid-gut which succeeds, possesses 

 a glandular dorsal diverticulum, and receives ventrally the 

 paired orifices of the two or four " liver " tubes (much reduced 

 in the Phronimidae). A pair of tubular glands, endodermal in 

 origin, open at 

 the posterior 

 end of the 

 mid -gut, in 

 the Gam - 

 marina. Their 

 supposed e x - 

 cretory nature 

 is very doubt- 

 ful, as they 

 may be much 

 reduced in size 

 in that group 

 and are not 

 found in the 

 other divisions 

 of Amphipods. 

 On the other 

 hand the an- 

 tennary gland, 

 the equivalent 

 of the green 

 gland of De- 

 capods is pre- 

 sent, its Coiled FIG. 307. Phronima sedentaria. a female ; 6 male ; A', A" first and 



second antennae ; D intestine ; Dr glands in the chela of the fifth 

 duct Opening leg ; G genital orifice ; H heart and aorta ; K branchiae ; Kf mandible ; 



N nervous system ; eye (upper portion) ; Ov ovary (after Claus). 



at the base of 



the second antenna. 



In the Corophiidae groups of unicellular glands are present 

 in the third and fourth thoracic appendages, on the terminal 

 claws of which they open. Their secretion is used in con- 

 structing the tubular dwellings of this family. 



The heart lies in the thorax in a pericardial sinus, with which 

 it communicates by three (or fewer) pairs of lateral ostia ; and 

 z in K K 



