46 THE APODID^: PARTI 



was needed both for locomotion and for the purpose of 

 grasping and bringing prey towards the middle line. 

 This bending round of the dorsal parapodium towards 

 the ventral middle line naturally leads to its greater 

 development, at least in the anterior limbs, which 

 function as described ; in the posterior limbs, which 

 have only to assist in swimming, the dorsal branch is 

 not so highly developed, forming with the ventral the 

 swimming plate (Fig. 10). 



The anterior limbs are the most highly differentiated 

 from the original parapodia, they are the most 

 Crustacean. On the principle of the division of 

 labour, we find the first limb almost entirely specialised 

 as a sensory limb. Its appendages, omitting the 

 ventral parapodium, formerly considered as an 

 appendage of the limb, are, on the inner side, feelers 

 (called endites) with tufts of sensory hairs on slight 

 protuberances, which are regularly arranged alter- 

 nately on the two sides (see Fig. 9). The feelers vary 

 in length in different species, and are of importance 

 in classification. The corresponding appendages on 

 the other limbs are leaf-shaped plates with highly 

 developed denticulate setae 1 on their flat surfaces, and 

 tufts of sensory hairs along their edges. Besides 

 helping in swimming, these sensory endites have 

 been specially developed to assist in the capture of 

 prey. The action of sweeping together prey into the 

 middle line by means of the long dorsal parapodia, 

 requires a fine sense of touch on the under edges of 

 the limbs. The denticulate hairs at the sides of the 



1 See Fig. 5. 



