i6o 



THE 



PART I 



for the most part crawl, and develop " auditory ' 

 organs in the antennules. 



We may in this connection mention the frontal 

 sensory organs which appear in many (or all ?) Nauplii 

 (see Fig. 39, f) on each side of the unpaired eye. 

 They disappear throughout nearly the whole class 

 in the course of development. They may perhaps 



FIG. 38. Nauplius of A. cancriformis just hatched, dorsal view (after Claus). 

 S, posterior edge of the shield ; N, the large larval excretory organ, the dorsal 

 or neck organ. 



be supposed to represent a pair of feelers rising on 

 the prostomium of the original Annelids, such as those 

 found, for example, on the prostomium of the Eunicidae. 

 In a section of Apus cancriformis we thought we found 

 traces of them on the frontal surface in a very 

 short stiff horn-like process of the cuticle, at the base 

 of which was a group of large ganglion cells. 



