38 Journal of Comparative Neurology. 



of these organs is composed of oblong nucleated cells, which 

 are arranged with their longest axes perpendicular to the 

 hirsute surface [fig. 4]. The organs in the upper lip are 

 innervated by a branch of the labial nerve, those in the man- 

 dible by a branch of the mandibular nerve and those in the 

 lower lip, by the labral nerve [fig. 16]. Thus we have, sur- 

 rounding the mouth, three pairs of similar sense organs. 



I have no definite proof as to the function of this set of 

 organs ; but, since they surround the mouth, they probably 

 function as food discriminators. Whether this discriminating 

 sense is one of touch or taste I am not prepared to state. 



Auditory Organ. — After describing rather minutely what 

 he considers to be a sense organ located at the tip of the second 

 foot, Dr. Rehberg expresses his belief that that organ is an ear. 

 Now I agree with Dr. Rehberg in believing that there is a sense 

 organ located in the tip of the second foot ; but I think that its 

 function is not auditory but tactile. I do not think that the 

 structure of the tip of the second foot warrants Dr. Rehberg's 

 assumption. And beside, at the base each of the antennules I 

 have found what I consider the auditory organ of Cypris [fig. 16, 

 £"]. This is an ellipsoidal body in the centre of which there is 

 a sac. The space between the outer wall of the ellipsoid and 

 the sac is occupied by a single layer of columnar cells. The 

 nuclei of these cells are located near the periphery. These cells 

 are best seen in transverse sections of the organ [fig. 33]. 

 Often the cells contain large vacuoles [fig. 29]. Within the sac 

 there is a small spherical body which I take to be an otolith 

 [fig. 29]. Since in most of my preparations this sac has been 

 filled with a deposit of the stain used [fig. 33] I am not sure 

 that this spherical body that I find in other preparations is an 

 otolith or merely a bit of stain. 



As to the innervation of this organ, I have no definite 

 knowledge. However, the antennary nerve is so intimately 

 associated with this organ [fig. 29^], that I am inclined to be- 

 lieve that that nerve innervates the auditory organ. 



There are two patent facts that lead me to hold that this is 

 an auditory organ: 1st, in histology it resembles an otocyst ; 



