HEARING- AND ALLIED SENSES IN FISHES. 
57 
containing a thin, flat otolith of considerable size. Sometimes this otolith is repi’e- 
sent.ed by two pieces — -a small one at the anterior end of the sacculus and a much 
larger one occupying the more central part of this chamber. The lagena, which is 
well separated from the sacculus, also contains an otolith. On the median face of 
the sacculus is an extensive macula acustica sacculi, formed by the termination of 
the major part of the eighth nerve. There is also a well-developed papilla acustica 
lageme, as well as the usual three crista; acustica; ampullarum. I am unable to 
state whether other sensory patches, such as the macula acustica neglecta, occur 
here or not. 
Having made a preliminary study of the anatomy of the internal ear, I had hoped 
to be able to cut in different individuals different branches of the eighth nerve, and, 
by further experimentation on fishes thus prepared, to determine the functions of 
the several sense organs of the internal ear. After numerous unsuccessful attempts 
I was at last obliged to abandon this plan because of the small size of the branches 
and their somewhat intricate relations, and I am, therefore, in possession of no 
observations that show which part or parts of the internal ear are concerned in 
hearing. 
THE LATERAL-LINE ORGANS AND THE SKIN. 
Introductory . — The lateral-line canals were regarded by most of the earlier 
investigators as glands for the production of the mucus so characteristic of the skins 
of fishes. About the middle of the last century Leydig (1850, p. 171) discovered the 
numerous sense organs contained in these canals, and declared that the whole system 
represented a sensory apparatus peculiar to fishes. Subsequently Leydig (1868, 
p. 2) expressed the opinion that these organs implied the possession of a sixth sense, 
one in addition to the five usually attributed to vertebrates, though he admitted that 
this sense was probably closely related to touch. Two years later the lateral-line 
organs were investigated by Schulze (1870), who demonstrated that true lateral-line 
organs ivere found only in the water-inhabiting vertebrates. From a study of their 
structure Schulze (1870, p. 86) was led to the belief that they were stimulated by 
the mass movement of the water, as when a current passes over the surface of a 
fish or when the fish swims through the water. He further believed that they were 
stimulated by sound waves whose length was greater than that of waves to which 
the ear was adapted. In this respect they were organs somewhat intermediate in 
character between those of touch and of hearing. These opinions were opposed by 
Merkel (1880, p. 5-1), who pointed out the inaccessibility of the organs to moving 
water in many cases, and who regarded them merely as organs of touch. The 
opposite extreme was taken by P. and F. Sarasin (1887-1890, p. 54), who designated 
them accessory ears, a view suggested some years previously by Emery (1880, p. 48). 
The opinions thus far given were based for the most part on an interpretation 
of the anatomy of the lateral-line organs, and not upon any positive experimental 
evidence as to the function of these parts. Fuchs (1895, p. 467) seems to have been 
the first to attempt work in this direction. His experiments were made chiefly on 
the torpedo, a fish in which, in addition to the lateral line proper, two other sets or 
organs, the vesicles of Savi and the ampulla; of Lorenzini, may be regarded as parts 
of the lateral-line system. In an active torpedo Fuchs cut the nerves connected with 
these two special sets of organs without, however, being able to detect any significant 
change in the subsequent movements of the fish. He then exposed the nerve inner- 
vating the vesicles of Savi, and having placed it in connection with the appropriate 
