DEVELOPMENT, GELASIMUS AFTER HATCHING 493 



The two basal segments are very short, the terminal segment is 

 like the terminal segment of the endopodite of the first maxilliped. 



The abdomen is composed of five movable segments. Each 

 of the first four is cylindrical and of approximately the same 

 diameter. They increase slightly in length from the first to the 

 fourth. The second, third, and foiu"th segments are produced 

 backward and laterally into an angular process which slightly 

 overlaps the next succeeding segment. The posterior border of 

 each of these segments bears a median seta dor sally. The sec- 

 ond segment bears a short blunt lateral spine which curves for- 

 ward. It is so placed that its curvature serves as a groove into 

 which the posterior border of the carapace fits. The third seg- 

 ment also bears a spine which curves backward on each side and 

 is less conspicuous. The terminal segment represents the sixth 

 abdominal segment fused with the telson. It is crescent-shaped 

 with the horns elongated. The anus lies on the ventral surface 

 of this segment. It is surrounded by very tumid, movable lips, 

 which may form a protuberance as in figure 1. From the median 

 surface of each horn near its base, three setae arise which are 

 plumose with short stout hairs. The length of the segment with 

 its horns is 0.22 mm. 



First zoeal stage of G. pugnax (figs. 3 and 4) . The first zoea of 

 (;. pugnax differs from that of G. pugilator only in size. It is 

 smaller in all dimensions. The anterior and dorsal spines are 

 shorter and slenderer. Otherwise there is the most absolute 

 identity in pigmentation and conformation of the appendages — 

 even to the number and kind of hairs found on each. 



First roeal stage of G. minax (figs. 5 and 6). The first zoea of 

 G. minax is distinguishable from that of G. pugnax with the 

 greatest difficulty. It is slightly smaller, but shows the same 

 slender spines of the carapace. 



The first zoeal stage of Gelasimus (figs. 1 to 6) is most readily 

 distinguished by the four plumose hairs of the exopodites of the 

 maxillipeds. The caudal portion of the scaphognathite is a single 

 elongated conical process thickly beset with fine hairs. 



The second zoea (figs. 7 and 8) has increased in length to 1.175 

 mm. The eyes are on stalks and are slightly movable. The 



