GENERAL ANATOMY. 17 



running obliquely outwards each branch of the fork 

 subdivides into two, an anterior and a posterior 

 branch, both sensory. At the commencement of the 

 third abdominal segment the ventral cord forks, its 

 branches diverge slightly in this segment, but more 

 in the next, rising to the sides of the intestine, and 

 having the ventral muscles of this segment superficial 

 to them. In the last segment they have left the 

 intestine and run about the horizontal median plane 

 straight into the axis of either branch of the f urea. 



" The ventral cord in Cyclops is not differentiated 

 into distinct ganglia up to the second free (third) 

 thoracic segment : beyond this is an enlargement con- 

 taining ganglion cells at the posterior end of the 

 fourth, and another (very small) in the last thoracic 

 segment." 



THE ORGANS OF SENSE, so far as they exist in the 

 tactile and olfactory rods of the antenna?, have already 

 received brief notice. Mr. Hartog has recently de- 

 scribed certain vesicles in the frontal region of Cyclops, 

 and others attached to the bases of the fifth pair of 

 feet and seated on a ganglionic enlargement of the 

 nerve supplying the feet, which vesicles he believes to 

 be auditory organs. In the male they contain one 

 or more highly refracting bodies floating freely in the 

 interior. Claus found a pair of these vesicles in the 

 brain of Calanella, and has figured them in * Die frei 

 lebenden Copepoden ' (plate vii, fig. 9). 



THE DIGESTIVE CANAL has a short, straight gullet, a 

 large stomach, often with two ca3cal tubes, and an 

 intestine opening on the dorsal aspect of the last (or 



VOL. in. B 



