DEVELOPMENT OF E. LONGIROSTRIS 291 



The thoracic Hmbs of a specimen 6-5 mm. long are as follows: 

 First limb. Endopod longer than exopod but still of two segments. 

 Second and third limbs. Endopods long and kneed. Gills of two branches. 

 Fourth limb. Endopod shorter but kneed. Gill of two branches. 

 Fifth limb. Endopod short, of three segments. Gill of two branches. 

 Sixth limb. A low bud, not bifurcating but budding off a gill. 

 Seventh limb. A gill of two branches. 

 Eighth limb. A small undifferentiated bud. 



There are no denticulations along the edges of the pleura of the abdominal somites. 

 The tergal wings of the first somite are very strong. The spine of the third is about 

 three-quarters the length of the fourth somite. The posterior margin of the telson is 

 narrow and straight with seven terminal spines. The innermost of the postero-lateral 

 spines is now the longest ; it has a thick base, and where it narrows distally on the inner 

 margin there is a row of strong spines. 



Furcilia, stage V (Fig. 39 //, /) 



Description based on the examination of six specimens, y-o-yy mm. long. 



I have regarded the six specimens with six, five or four spines on the telson (see list 

 on p. 286) as belonging to one group, and the description given below is based upon 

 them. Their antennal endopods are segmented and they appear to be at roughly the 

 same stage of development. Their lengths are as follows : 



With six terminal spines : i specimen, 7-0 mm. 



With five terminal spines: 2 specimens, both 7-5 mm. 



With four terminal spines: 3 specimens, 7-0, 7-4 and 7-7 mm. 



I have little doubt, by analogy with the other species described here, that if large 

 numbers of this stage were taken the majority would be found to have five terminal 

 spines on the telson. 



The dorsal organ is prominent. The frontal plate is as in the previous stage, but the 

 rostral spine is longer, reaching nearly to the end or to the end of the second segment of 

 the antennular peduncle. There are no denticulations along the lateral margins of the 

 carapace (Fig. 39 //). The posterior projection of the carapace reaches from more than 

 halfway down, to beyond the end of, the second abdominal somite. 



The antennular spine is as long as the sum of the second and third peduncular seg- 

 ments ; the lappet of the first segment is not developed. The mandibular palp is small 

 and unsegmented. 



The thoracic limbs of a specimen 7-5 mm. long are as follows: 



First limb. Endopod of five segments and over twice as long as exopod. 



Second limb. Endopod long and kneed. Gill of two larger and one smaller branch. 



Third limb. Endopod long and kneed. Gill of two large and one very small branch. 



Fourth limb. Endopod shorter but kneed. Gill as in third limb. 



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