152 



THE 



PART I 



claim that these in any way resemble the original 

 limbs of the primitive Crustacean. It is only neces- 

 sary to assume that they are homologous with the 

 first three pairs of Crustacean limbs, but modified for 

 the special needs of a free-swimming larval life. As a 

 matter of fact we do find that the form of the limbs 

 can easily be traced to its origin. The first uni- 

 ramose limb corresponds with the antenna of the 



.- 



FIG. 34. Nauplius of Apus cancriformis just hatched (after Claus). The large 

 rowing limb homologised with the dorsal parapodium d, carrying the sensory 

 cirrus c, which forms the most important branch, the smaller branch being the 

 tip of the parapodium. 



Annelids, i.e. with the sensory cirrus of the vanished 

 parapodium of the first segment. It arises direct 

 from the body as a uniramose appendage without 

 any parapodial portion, i.e. unless the slight bulging, 

 which is seen at its base in Apus (see Fig. 7 A, 

 p. 34) represents the remains of such a dorsal 

 parapodium, which we think improbable, as the 

 sensory cirri of Annelidan parapodia frequently rise 

 from such papilla-like swellings. Owing to the 



