194 Journal of Comparative Neurology and Psychology. 



us to determine that this blank neuromere is the one following 

 that which gives rise to the cerebellum, while in higher verte- 

 brates it is the second one behind cerebellum. 



5. Typical sense organs of vertebrates. 



According to the recent work of Dogiel (24), Amphioxus 

 possesses sense organs which in structure are comparable to the 

 sense cells of invertebrates on the one hand and on the other 

 to the olfactory organ of craniates. Sense cells of similar kind 

 have since been described by Marenghi (88) for Petromyzon. 

 From his own study of the epidermis of Petromyzon the writer 

 is led to think that Marenghi's interpretation of these elements 

 is more or less doubtful. The discovery, however, if it should 

 prov^e correct, is most interesting and important and confirma- 

 tion of Marenghi's description is very much to be desired. 

 All other sense organs of craniates are apparently distinct from 

 any found in acraniates or invertebrates ; namely, eye. pineal 

 org'ans, ear and lateral line organs, and end buds or taste buds. 

 The specialized sense organs found in higher vetebrates need 

 not be considered here. 



The literature on the morphology of the sense organs in 

 the skin and mucosae has been reviewed elsewhere (70), with 

 the result of showing that they fall into two categories : the end 

 buds and taste buds belonging to the visceral sensory division, 

 and the neuromast organs (ear, canal and pit organs, amp\illae, 

 Savi's vesicles) belonging to the cutaneous or somatic sensory 

 division. A reprint of the evidence on which this analysis is 

 based would be out of place here, but as some new facts and 

 discussions of this subject have since appeared it will be of use 

 to print a tabular comparison of all cutaneus organs, their func- 

 tions and nerve connections. The table is on an adjoining page 

 (Table A). 



The suggestion has been made by Allis (4, 5) and Coggi 

 (19, 20, 21) that the ampullae of Lorenzini are homologous 

 with the end buds of teleosts. Three supports are offered to 

 this hypothesis. One is based on the assumption that the cen- 

 ter for fibers supplying ampullae in selachians is the same as 



