254 



S. I. Smith — Early Stages of the American Lobster. 



Fig. 3.* 



much larger and slightly longer than the outer branch, or exognathus, 

 which is quite slender. 



The five pairs of cephalothoracic legs {g, A, /, figure 1, and a, b, 

 figure 3) are all similar and of about the same size, except the main 

 branch of the first pair, {g, figure 1, and a, figure 3,) which is much 



larger than that of the others, but is 

 still sack-like and entirely without ar- 

 ticulations. The outer or exopodal 

 branches of all the legs are slender, 

 wholly unarticulated, sack-like processes, 

 while the inner or main (endopodal) 

 branches of the four posterior pairs are 

 similar, but much stouter and slightly 

 longer processes arising from the same 

 bases. The bases of all the legs are 

 marked with dendritic spots of red pig- 

 ment like those upon the lower margin 

 of the earapax. 

 The abdomen (m, figure 1) is curved round beneath the cephalo- 

 thorax, the extremity extending between and considerably in front of 

 the eyes. The segments are scarcely distinguishable. The telson 

 (figure 4) is fully a third of the entire length of the abdomen, and, as 

 seen from beneath the embi-yo, is slightly ex- 

 panded into a somewhat oval form, and very 

 deeply divided by a narrow sinus, rounded at 

 the extremity. The lobes into which the tail 

 is thus divided are narrow, and somewhat ap- 

 proach each other toward the extremities, where 

 they are each armed along the inner edge with 

 six small obtuse teeth. 



The heart {I, figure 1) is readily seen, while 

 the embryo is alive, by its regular pulsations. 

 It appears as a slight enlargement in the dorsal 

 vessel, just under the posterior portion of the 

 earapax. The intestine {k, figure 1) is distinctly 

 visible in the anterior portion of the abdomen as 

 a well defined, transparent tube, in which float 

 little granular masses. This material within the 

 intestine is constantly oscillating back and forth 

 as long as the embryo is alive. 



* First and second cephalothoracic legs, as seen detached from the body and under 

 compression, enlarged 40 diameters : a, leg of the anterior pair ; b, leg of the second pair. 



f Extremity of the abdomen, seen from above and slightly compressed, enlarged 30 

 diameters. 



