6 Mr. C. S. Bate on the Morphology of some Amphipoda 



veloped beyond the first two joints of each of the rami ; three 

 posterior more matured, consisting of a peduncle and two sharp 

 styhform rami. Telson narrow and rounded. 



The points in which the larva appears to differ most conspi- 

 cuously from the parent are : — In the form of the cephalon, 

 which is a broad ovate ball in the adult (the lateral walls 

 encroaching upon the under surface and hiding both pairs of an- 

 tennae), while in the early form it is long and narrow, tapering 

 to a point, near which, on the under surface, the superior antennae 

 are planted, while the inferior pair are a little posterior to these : 

 though small, neither are covered by the lateral walls of the 

 cephalon. The pereion in the parent is broad and flat, and the 

 pleon considerably narrower, while in the larva they are both 

 uniformly narrow throughout the entire length of the animal, 

 tapering gradually towards the posterior extremity. The gnatho- 

 poda in the adult are complexly subchelate ; while in the larva, 

 if they can be said to assume ever so slightly the subchelate 

 character, it is by the dilated form of the propodos, which, 

 though broader at the distal extremity than the nearer, is not 

 more in diameter than half the length of the dactylos, and 

 therefore its prehensile capability must be feeble. The carpus, 

 which in the adult is developed into a large projecting process 

 that assists materially in perfecting the grasping power of the 

 appendage, is in the larva rounded- off and not developed, the 

 point of development being occupied by a solitary hair : a similar 

 hair exists also upon the infero- anterior angle of the preceding 

 joint. The first two pairs of pereiopoda, in the larva, may be 

 recognized as the undeveloped future organs, differing as they do 

 only in their more imperfect condition, being destitute merely of 

 some of the adult armature. The two succeeding pairs of pereio- 

 poda, which are developed upon one type, in the adult differ in 

 their proportions, so as to appear to vary considerably in form, 

 while in the larva they are uniform with each other in every 

 respect; they differ from those of the parent in having their 

 basa less developed, and the remaining joints considerably longer 

 in relative proportion both to the size of the basos as well as to 

 that of the animal. The fifth pair of pereiopoda in the adult 

 are obsolete, being represented by a flexible membrane only, 

 whilst in the young creature they are long, strong, and nor- 

 mally developed, like the previously described poda, except the 

 peculiar and curious dactylos. In the adult, the three posterior 

 pairs of pleopoda are membranous and foliaceous ; but in the 

 larva the rami are slender, sharp- pointed, and styliform. The 

 telson, in the adult, is as broad at the base as the preceding 

 segment of the pleon ; in the larva it is much smaller. 



