25^! 8. I. Smith — Early Stages of the American Lobster. 



tary. The endognathus (fig. 6, (() is only sparsely anued with stoiit 

 setae along and near the inner margin. The two segments of the 

 mesognathiis (fig. 6, h) are about equal in length, the hasal one with 

 two long simple seta^ on the inner side at the distal extremity, and 

 the terminal one with four at and near the tip. Of these terminal 

 setoe (fig. 6«, enlarged 100 diameters) the longest about eqxials in 

 length the terminal segment of the mesognathus itself and arises 

 from an emargination on the inner side close to the tij), two, 

 successively shorter, arise from the tip itself, while below the base of 

 these is one still shorter. The exognathus (fig. 6, c) is not longer 

 than the mesognathiis, shows no segmentation, the outer edge is fur- 

 nislied with twelve to fifteen jointed, plumose setae (fig. 6 5, enlarged 

 200 diameters), and at tip with two very short seta^, while the inner 

 edge is naked. The epignathus (fig. 6, d) is small and naked, the 

 posterior portion, though much longer than the anterior, is propor- 

 tionally very much smaller than in the adult, and the extremity is 

 rounded and j)roduced at the inner angle. 



The second maxillipeds (plate XVI, fig. 9, enlai-ged 40 diameters) 

 are not flattened and appressed to the inner mouth organs as in the 

 adult. The endognathus is stout and cylindrical, the last three seg- 

 ments are bent inward at nearly a right angle, and all the segments 

 have about the same proportional lengths as in the adult. The inner 

 sides of all the segments below the meral are armed with a few nearly 

 straight setiform spines, while the cai-pal segment upon the outer side, 

 and the succeeding ones all round, are sparcely armed with rather 

 stout spines, some of which are minutely serrate ; the terminal spine 

 is much stouter than the others and curved toward the tip. The 

 exognathus (fig. 9, «) is slender, rudimentary, composed of a single 

 article, does not reach beyond the meral segment of the endognathus, 

 and is furnished at the extremity with a very few sh(n-t and rudimen- 

 tary setae, two of which are at the tip and two or three more arise 

 from slight emarginations in each side, thus showing a very slight 

 approach to the flagelliform character wiiich this appendage has in 

 the adult, although there is as yet no indication of segmentation, 

 even at the tip. The epignathus (fig. 9, h) is rudimentary and sack- 

 like, scarcely longer than the diameter of the segment from which it 

 arises, and is apparently without a branchial appendage. 



The external maxillipeds (plate XVI, fig, 18, enlarged 25 diameters) 

 are elongated and pediform, the endognathus being as long as and 

 much like the endopodi of the posterior legs, while the exognathus is 

 like the exopodal branches of all the legs. The segments of the 



