576 MEMOIRS OF THE :national acade.aiy of scie>-ces. 



Platk LVII. 



(Stage XII.) 



Figs. 236-245. Horizontal sections of lir.st larva, illustrating further the anatomy of the alimen- 

 tary tract and the nervous system. x57. 



KEFERKNCE LETTERS. 



J. /, U, first auil second autenua. 



ag.. green gland. 



ttf., autennular tiber-niass. 



10., ear. 



hij., branohiostejfite. 



End., eudoderiii. 



/(/., foregut. 



/<)., liber-substance of tesophageal commissure. 



ijf.. liber-mass of second antennae. 



gg. '-', middle, ventral, and dorsal divisions of posterior lobe of midgut. 



kg., hindgnt. 



//., lateral tibermass of brain. 



Mil., mandible. 



Mg., midgut. 



ilg.\ lateral lobe of midgut. 



Mp., partition between anterior lobes of midgut. 



-)/(«., metastoma. 



Mjc.I, II, first and second maxillae. 



Mxpd. I-III, first to third maxillipeds. 



II. an., antennular nerve. 



li.c, ventral nerve-cord. 



of., anterior fiber-mass of brain. 



og., optic ganglion. 



lirt., retina. 



J^'l'- i-^, first to fifth aiul.nlalory limbs. 



y., yoik. 



