218 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
a single fibril from one neuron into another. If such a connection 
between nerve elements had been demonstrated beyond a doubt, they 
might still be considered as distinct trophic units, and the interdigitating 
fibrils uniting them as the products of separate neuron cells. In the light 
of the important discoveries of Apathy and Bethe, however, the old 
view, that the nervous impulses are transmitted from sensory to motoi 
neurons by the simple contiguity of their dendritic processes, may have 
to be abandoned for the more reasonable assumption of direct fibrillar 
communication. 
PART II.— PHYSIOLOGY. 
As Bethe has well said, the best of anatomical knowledge concerning 
an organ cannot be taken as certain evidence of its functions. It is 
only after these functions have been experimentally demonstrated, that 
we may ascribe them with confidence to the organ in question. 
Have we, then, any experimental proofs that the decapod Crustacea 
hear? If so, is the otocyst the auditory organ ; if not, what is its func- 
tion? These are the three chief questions which I shall attempt to 
answer. 
A. HISTORICAL SURVEY. 
Up to the time of Delage (’87) the auditory function of the otocyst 
was accepted, and that alone. 
Minasi (1775) promulgated the idea that Crustacea could hear. The 
hermit crab, Pagurus, was more sensitive than man to sound vibrations, 
The tones of a distant bell, the striking of a clock, were, according to 
this worthy monk, perceived by Pagurus sooner than they were by 
him. 
Alianus (1784) notes that the fishermen of his time took Pagurus 
by means of music, 
All the older zodlogists have regarded the otocyst as an organ of 
audition. 
Hensen (63) was the first to get experimental data. From the 
anatomical conditions found in the otocyst of the lobster, he argues as 
follows: Here are 468 auditory hairs upon which otoliths rest. Of 
these hairs no two are of the same size ; they vary in a nearly continu- 
ous series from 0.72 mm. to 0.14 mm. in length; thus the volume of 
the largest is to that of the smallest as 140: 1. Comparing these 
