216 bulletin: museum of comparative zoology. 



The opposition to the neurone theory has been based largely upon 

 investigations of the conditions in the neuropile of central organs, 

 where Apathy, Bethe, and others maintain that there is an intimacy 

 of relations which is incompatible with the neurone theory. Prentiss 

 (:03, :04) and Dogiel (:05) have also described conditions in periph- 

 eral nervous organs which would seem to demand the radical modifi- 

 cation, if not the abandonment, of the neurone theory. 



The present paper bears on the general problem of the validity of 

 the neurone theory. The two cardinal questions for which I have 

 undertaken to find answers are these: How are the terminal fibres 

 of the eighth cranial nerve in fishes related to one another, and how 

 are they related to the cells of the sensory epithelium in the ear sac ? 

 A condition of true anastomosis between terminal fibres of different 

 axis cylinders would evidently be inconsistent with the neurone theory, 

 whereas the absence of such anastomoses would tend to confirm the 

 theory. Furthermore, a condition of organic union between sense cells 

 and axis cylinders which are connected with cell bodies elsewhere 

 would obviously be out of harmony with Waldeyer's conception, since 

 he regarded the axis cylinder as an outgrowth from the ganglion cell, 

 and a dependency of it both anatomically and physiologically. Simple 

 contact, on the other hand, between sense cell and axis cylinder would 

 be quite in accord with the requirements of the neurone theory. 



II. Historical Review. 



The relations of the terminals of the eighth cranial nerve have long 

 been a subject of interest to histologists. The early work has been 

 adequately reviewed by J. Kishi (:01), Retzius (:05^), Kolmer (:07), 

 and Bielschowsky und Briihl (:07), and requires only brief mention 

 here. Among those who contributed to this early literature were 

 KolHker ('54), Max Schultze ('58), Waldeyer ('72), Meyer ('76), and 

 Retzius ('71, '81^, '94). By the use of simple stains and isolation 

 methods these investigators were led to believe that the fibres of the 

 eighth nerve end in the protoplasm of the hair cells, fibre and cell being 

 continuous. The cell was regarded as the end organ of the fibre. 



The application of the Golgi and the methylene blue methods to the 

 problem resulted in a general reversal of this view. Retzius ('92, 

 '93, '94), van Gehuchten ('92), von KoUiker ('92), and von Len- 

 hossek ('93) came to regard the hair cells as secondary sense cells, 



