AMERICAN PALASITIC ARGULTD.^^WILSON. 



667 



\n foliaceus and catoxfoiiii thoy aro armed with a chiw on their pos- 

 terior border whieh reaches outside tiie lower lip, and are separated 

 l)y the side walls of the mouth from the mandil)ular palps already 

 described. In the incgtilopx and sfhostethn larvse there are no palps 

 and no claw reaching- outside the lower lip, so that the mouth assumes 

 almost exactl}' the structure of the adult, save for the lack of max- 

 ilhv (tio-. S). 



With regard to the histology and internal structure, that portion of 

 the intestine immediately behind the mouth and reaching into the first 

 free thoracic segment is somewhat wider than the remainder and is 

 sharply marked oti' from it b}^ a constriction in the side walls and b}^ 

 much darker coloration. This is the stomach of the larva, and it sends 

 out on either side a wide liranch toward the edge of the carapace just 



Fig. 8.— Chitin skeleton of the proboscis of a newly hatched megalops larva, c. Chitin 

 framework; /., LOWER LIP; //., labial palp; md., mandible: mx., maxilla. 



behind the posterior maxillipeds. (Plate VIII.) The branches turn 

 both backward and forward inside the edge, like a section of the stem 

 and umbrella of a mushroom, and are crenated along their outer 

 ])order. Both central portion and branches are so tilled with yolk 

 granules and oil globules as to be nearly opaque. 



The remaining portion of the intestine in the free thoracic segments 

 is somewhat narrower and is filled with much clearer cells. In the 

 last segment it passes abruptly into a narrow cloacal portion which 

 runs through the center of the abdomen as a narrow tube, and ends 

 in the anus, which is a transverse slit situated just beneath the papillte 

 at the base of the anal sinus. All three parts of this digestive tube 

 keep up a lively contraction, l\y means of which there is frequent 

 interchange of their contents. 



