DEVELOPMENT OF E. FRIGIDA 269 



Fourth limb. Considerably shorter than third, bifurcated, with endopod unsegmented 

 and without or with terminal setae, a strong gill bud. 



Fifth limb. Very short and not bifurcate, or bifurcate, a small or a strong gill bud 

 (Fig. 36 k). 



Sixth limb. A low unbifurcate bud, no gill bud or a small gill bud. 



Seventh limb. Very rarely no gill bud, usually a small or a strong gill bud. The 

 seventh gill bud appears before the sixth and is always bigger than it in this and the 

 stages which immediately follow. 



Eighth limb. Usually not developed, very rarely a small gill bud. 



The tergal wings of the first abdominal somite are not connected dorsally by a collar 

 as in this stage of E. vallentini. 



Of the 239 specimens examined all but two had seven terminal spines on the telson ; 

 the two had five. 



Furcilia, stage IV (Fig. 36 /, m, n) 



Description based on the examination of twenty-three specimens. Eighty were measured and 

 were 6-5-77 ™n^- long. 



In this stage there are five pairs of setose pleopods, the antennal endopod is segmented 

 and there are five terminal spines on the telson. 



The carapace has a low and well-defined ridge, an ill-defined ridge, or more rarely no 

 ridge, in the position of the dorsal organ. The frontal plate is rarely broad and evenly 

 rounded with no central point, or triangular with strongly convex sides and a central point, 

 or a sharply pointed triangle with feebly convex or straight sides (Fig. 36 /, m, n). 



The antennular spine reaches up to halfway along the third segment of the peduncle. 



The mandibular pulp is usually not segmented, rarely segmented. 



The degree of development of the thoracic limbs is as follows : 



First limb. Short. Endopod mostly with three, sometimes with four, rarely with 

 five, segments. No gill bud. 



Second limb. Endopod long and kneed. 



Third limb. Endopod nearly as long as that of second, not kneed or feebly kneed. 



Fourth limb. Endopod considerably shorter than that of third, divided sometimes 

 into three, more usually into five segments. 



Fifth limb. Bifurcate. Endopod rarely very short with only one or two terminal 

 setae, most frequently longer with many setae but unsegmented ; rarely segmented. 



Sixth limb. Either a low bud beginning to bifurcate or short and bifurcate with no 

 setae on endopod. 



Buds of the second to eighth pairs of gills are present, usually unbranched, the seventh 

 slightly bigger than all the others, the eighth sometimes very small. The sixth to eighth 

 pairs may be beginning to branch ; the seventh appears to be the first to show signs of 

 branching. 



The tergal wings of the first abdominal somite are not connected dorsally by a collar. 



