3f)4 MEMOmS OF THE NATIONAL ACADEMY OF SCIENCES. 



and those of the first ami second thoracic legs. The eudopodites of the maxillipeds are as before. 

 The endopodite of the first thoracic leg, which was represented iu stage three by a rudimentary 

 bud, now appears to be entirely wanting. The second thoracic limb, which in stage three was 

 represented by a bilobed bnd, now consists of a basal joint, with a large, functional, plumose 

 exopodite and a rudimentary, bud-like endopodite. Between this appendage and the base of the 

 fidly developed fifth thoracic limb there is a row of buds to represent the third and fourth thoracic 

 limbs, which became developed after the next molt. The fifth is about as it was in the preceding 

 stage, and it carries no trace of an exopodite. The abdomen is about as before, except that the 

 endo])odite of the sixth abdominal appendage, the onlj' one yet represented, is now fully devel- 

 oped and fringed like the exopodite bj' long, plumose, swimming hairs. The telson has become 

 elongated and narrow, and the spiues uiiou its posterior end are much smaller than before. 



THE FIFTH LARVAL STAGE. 



None of the figures of the larvje of other species exactly represent the larva of Alpheus minor 

 after the next molt. The eyes are now partially covered by the carapace, and the swimming 

 organs are the seven pairs of fullj" developed exopodites belonging to the three pairs of maxillipeds 

 and the first four pairs of thoracic legs. At this stage these four pairs of appendages reacquire 

 their endopodites, and the anterior end of the body is similar to that of the larva shown in PI. xxi, 

 Fig. 1, from which, however, it differs greatly as regards the telson and the sixth abdominal ap- 

 ])en(l;ige. The first five abdominal appendages are now represented by buds like those shown in 

 PI. XXI, Fig. 1, and in PI. xix. Figs. 1 and 2, but the terminal portion of the abdomen is nearly like 

 that of Fig. 3 in PI. XX. The telson is greatly elongated, narrow, and its terminal spiues are 

 very small. 



THE OLDER LARYAL STAGES OF ALPHEUS MINOR. 



During the successive molts the abdominal appendages become fully developed, the eyes be- 

 come completely covered by the anterior edge of the carapace, the antennae become elongated, the 

 auteniiule develops a scale, the swimming exopodTtes of the maxillipeds and thoracic legs disap- 

 pear, these appendages assume their adult form, and acquire gills, and the animal gradually be- 

 comes like the one shown in PI. xx. Fig. 2, which is a young Alpheus of another species. 



THE METAMORPHOSIS OF ALPHEUS HETEROCHELIS FROM THE BAHAMA ISLANDS. 



In the Bahama Islands this species passes through a series of stages which, except for a few 

 minor diftereuces of detail, are exactly like those in the life history which has just been described. 



This fact is remarkable when it is known that the life history of the same species is very 

 different at Beaufort, North Carolina, and that Packard has described still another life history 

 for specimens of the same species which he studied at Key West. 



FIRST LARVAL STAGE. 



Tlie Bahama specimens hatch from the egg in the stage shown in side view in Fig. 1 of Pl.xviii. 

 As this larva agrees iu all details of its structure with the first stage of Alpheun minor shown in 

 PI. XVII, Fig. 2, already described, no further description is necessary. 



THE SECOND LARVAL STAGE. 



liike Alphens miniis the Bahama specimens of Alpheus heterochelis molt within a few hours 

 after hatching, but they undergo no essential change, and PI. xvi. Fig. 2, exhibits all the essential 

 characteristics, although this figure was drawu from a specimen oi Alpheus minor. 



The most noteworthy specific difference is in the relative length of the marginal spiues of the 

 telson. In the first and second larval stages of both species there are eight pairs of si>ines, one 

 ))aii- on the outer edge and seven on the posterior edge, as shown for Alphens minor iu PI. xvi, Fig. 2, 

 and for Alpheus heterochelis in PI. xvi. Fig. .3. In both s[)ecies the pair next the median line are 

 rudimentarj' and the next pair very small, but the tluee which arise from the rounded angle of the 



