490 O. W. HYMAN 



mus may be distinguished in two ways : the length of the antenna 

 does not equal that of the anterior spine in the case of Gelasimus, 

 but does in Sesarma; the first maxillipeds of Sesarma have 

 pigment spots at the proximal ends of the protopodites, while in 

 Gelasimus the first maxillipeds have pigment spots at the distal 

 ends of the protopodites. 



The pigmentation of all the zoeal stages of Gelasimus is re- 

 markably constant and serves as a ready means of establishing 

 the identity of the form. The pigment spots are jet-black when 

 contracted. In the expanded condition they vary in color, being 

 black or olive or red-brown or orange or combinations of these 

 colors. The distribution of the spots is as follows : on the cara- 

 pace, a spot posterior to the base of the dorsal spine, a spot on 

 each lateral flange of the carapace near its posterior angle, a 

 median spot between the eyes, a large spot on the front of the 

 base of the anterior spine, a spot between the bases of the first 

 and second maxillae; on the appendages, a spot on the labrum, 

 one on each mandible, and one on the distal border of the proto- 

 podite of each of the first maxillipeds; on the abdomen, a pair of 

 dorso-lateral spots between the first and second segments, a pair 

 of ventral spots on the second and third segments, and lateral 

 spots on each side of the posterior borders of the fourth and 

 fifth segments. 



DISTINGUISHING CHARACTERISTICS OF THE ZOEAL STAGES 



The first and second zoeal stages of the thi-ee species were ob- 

 tained with certainty by hatching and rearing them in the lab- 

 oratory. The distinctions between equivalent stages of the three 

 species, however, all proved to be relative differences of such slight 

 degree that I was never sure that I could separate certainly the 

 specimens obtained from the tow. Some specimens had the 

 characteristic broad-based, evenly tapering frontal spine of G. 

 pugilator and others the slender constricted spine of G. pugnax, 

 but many of them seemed intermediate, and I gave up the at- 

 tempt to distinguish the species. The different developmental 

 stages of the zoeae were easily distinguishable from each other, 

 however, as is indicated in the descriptions b'elow. 



