CHARACTERS OF THE CUMACEA 293 



creatures, and lie therefore found them.' Some years 

 earlier Milne-Edwards had indeed described a species as 

 having two eyes, which almost certainly has but one ; so 

 easily are even the ablest naturalists misled into taking 

 for granted that what is customary will prevail. A very 

 few of the Cumacea have two eyes. The majority have a 

 single median eye, but occasionally the elements of this 

 compound organ are so arranged as to have the appear- 

 ance of several distinctly separated ocelli. 



The Cumacea are said to leave the egg as maggot- 

 shaped Nauplii. From the maternal pouch they issue 

 almost in the adult form, only being as yet without the 

 last pair of trunk-legs or perasopods, a deficiency which 

 in two species, Campylaspis nodulosa, Sars, and Leptostylis 

 manca^ Sars, is perhaps persistent. The notion that these 

 creatures, which are in truth born almost fully fledged, were 

 only larval forms, was early disproved by Goodsir and 

 Kroyer, but was nevertheless still upheld for several years 

 by three of the most distinguished naturalists of the 

 century. 



In no group of the Malacostraca is the general form 

 more characteristic than here. This is principally due to 

 two unvarying features, the narrowness of the pleon and 

 the prominence of an elongate pair of uropods at its ex- 

 tremity. A distinct telson may or may not be present ; 

 of the six preceding segments none is ever wanting, and 

 of these the fifth, without any trustworthy exception, is 

 the longest. The front part of the body is always more 

 bulky than the pleon, and sometimes enormously so. The 

 integument is often stoutly crustaceous, more ready to 

 break than to bend. 



Normally there are five segments of the trunk distinct 

 behind the ca.rapace, carrying respectively the five pairs of 

 pergeopods. Occasionally, however, the first of these five 

 segments is absent or rudimentary, and in one genus the 

 third and fourth segments are coalesced. Sometimes the 

 carapace overarches one or more of the free segments. More 

 or less completely sheltered beneath the carapace lie all 

 the organs from the eyes to the third maxillipeds. There 



