Beport on Larval Crdbs. 7 



segment is now separated from the telson. The anus is partly attached to 

 the telson (fig. 20). The latter resembles the condition in I. Zoea, but 

 difiers in having a small hair on either side of the contained angle of the 

 fork. Each prong has three teeth on its external edge. 



The exopodites of the first and second maxillipedes had each eight setse. 



The tip of the rostral spine was in one specimen well curved down- 

 wards. Three pairs of little hairs were observed on the dorsal spine. 

 Some hairs were present on the free hind edge of the carapace. One was 

 much larger than the rest. 



A III. Zoea moulted into a lY. "Zoea. 



IV. Zoea, fig. 21 ; Abdomen, fig. 19; Telson, fig. 23. 



Size. — Distance between the tips of the rostral and dorsal spines, 2*9, 

 3 "2 mm. ; length of rostral spine beyond the eye, "95-1 ■! mm. 



The abdomen shows a farther development of the spinous prolongations 

 (fig. 19); they are now prominent, resembling in some degree similar 

 processes in the Zoea of Hyas. The stud was not now visible on the 

 third segment. A short hair was found in this stage on the dorsum of 

 the first segment. The pleopods now project as conical processes. 



The telson (fig. 23) has an additional pair of hairs at its contained angle. 



The exopodites of the first and second maxillipedes had each ten setae. 



The antenna now consists of three branches. The jointed branch with 

 its terminal spine is considerably shorter than the serrated branch. 



Five or six little hairs were made out on the dorsal spine. The hairs 

 were present also on the edge of the carapace. 



A lY. Zoea moulted into a Y, Zoea. 



V. Zoea, fig. 14; Abdomen, fig. 16; Telson, fig. 22; Antenna, fig. 22a. 



Size. — Distance between the tips of the rostral and dorsal spines, 

 3"9-4'4 mm.; length of rostral spine beyond the eye, ri-l"4 mm.; 

 length of dorsal spine, from posterior edge of carapace, 1"75 mm. ; distance 

 from the eye to the hind margin of the carapace, 16 mm. 



There is a close resemblance to the last stage. The pereiopods and 

 pleopods are now large, and the Zoea is much larger than stage lY. 

 The exopodites of the first and second maxillipedes have each twelve setae. 



The antennule has a large number of filaments, at least eleven. This 

 appendage has a small round branch. The third branch of the antenna 

 has increased in length. It was not so long as the serrated branch, but 

 very nearly equalled the jointed branch, including its spine. The latter is 

 much shorter than the serrated branch. Without its terminal spine the 

 jointed branch is less than half the length of the serrated branch. 



Four little hairs were found on the dorsal spine. The hind free edge 

 of the carapace has a f linge of long fine hairs. 



The abdomen is shown in side view in fig. 16. A pair of short hairs 

 was present on the dorsum of each of the first five segments. 



The telson (fig. 22) resembles that appendage in the previous stage. 

 The uropods are, however, larger. 



Y. Zoea cast into Megalops. 



The Zoea stages are characterised in each species by the progressive 

 development of the pereiopods and pleopods which became functional for 

 the first time in the Megalops. But in this species there is a secondary 

 Zoea character developed. The spinous processes from certain of the 

 abdominal segments are required for some function in the Ilf.-Y. Zoese, 

 but are not needed in I. Zoea. 



In Carcinus mcenas the hind border of the third, fourth, and fifth 

 abdominal segments is extended posteriorly into a triangular expansion. 



