DEVELOPMENT OF E. VALLEXTINI 275 



Fur cilia, stage IV 



Description based on the examination of ten specimens. Thirteen were measured and were 

 6-3-7-I mm. long. 



In this stage the antennal endopod is segmented and there are five terminal spines on 

 the telson. 



The carapace has a prominent and unmistakable dorsal organ, quite unlike anything 

 seen in this stage of E. frigida. The frontal plate is triangular with feebly convex or 

 straight sides. 



The antennular spine varies from being a little longer to a little shorter than the second 

 segment of the peduncle. The mandibular palp is unsegmented. 



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



First limb. Endopod varies from having more than two segments indicated to being 

 of five segments but not kneed; no gill bud. 



Second and third limbs. Endopods long and kneed. 



Fourth limb. Endopod of five segments, short and not kneed or longer and feebly or 

 strongly kneed. 



Fifth limb. Varies from being short unsegmented but setose to having an endopod of 

 five segments which is not kneed. 



Sixth limb. Usually very short and non-setose, rarely having an endopod with three 

 segments indicated or completely marked off. 



There are seven pairs of gills, the second to the eighth, present. They may all be of 

 single buds, the eighth pair small ; the second to fifth may be branching, the sixth and 

 eighth single ; the second to fourth may each have a small branch, the fifth be branching, 

 the sixth and eighth of two branches and the seventh of three. 



The collar joining the tergal wings of the first abdominal somite is not so high mid- 

 dorsally as in the previous stage but it is distinct and characteristic enough to serve to 

 distinguish this stage from the same stage of E. frigida. 



Furcilia, stage V 



Description based on the examination of thirty-five specimens for all but the development of the 

 gills for which twenty were examined. Forty-five specimens were measured and were 6- 1-7-6 mm. 

 long. 



In this stage there are three terminal spines on the telson. 



The carapace has a prominent and unmistakable dorsal organ which is, however, a 

 little lower in the larger specimens than in the smaller. The frontal plate is triangular 

 with feebly convex, or more often, straight sides. 



The antennular spine is usually as long as the second peduncular segment. The 

 mandibular palp is either unsegmented or of three segments and setose. 



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



First limb. Either short, the endopod having five segments indicated, or longer, the 

 endopod having five segments ; usually there is no gill bud but there may be one. 



