The brain of Acipenser. 185 
that they do. Acipenser has four long slender barbles dependent 
from the under surface of the rostrum in front of the mouth. These 
are innervated by communis components and, I suppose, are richly 
supplied with end buds as the barbles are in Amiurus. The barbles 
are dragged on the bottom as the fish swims slowly about in search 
of food. The presence of food in the aquarium produces evident 
excitement in the fish but his movements are entirely aimless, with 
the exception of a persevering hunt up and down the floor of the 
aquarium with the barbles. At the instant that these touch an 
earthworm or other suitable food body, the mouth is quickly pro- 
truded and the food sucked up. The reflex is rapid and unmistakeable. 
It is scarcely possible that it is a tactile sense by which the animal 
distinguishes between food and other bodies. The barbles are in- 
nervated by both cutaneous and communis components (GORO- 
NOWITSCH, ‘88, p. 481-—482). The cutaneous components are tactile, 
the communis components are gustatory. The buds situated on the 
fins and back in various fishes are in the best location to detect in 
the water chemical indications of the presence of food or of sub- 
stances which would be injurious to the respiratory function. The 
end buds on the fins would give earlier warning about either of 
these than could be received through the buds of the mouth and 
pharynx. Upon these grounds I believe that the hypothesis in 
question stands, so far as its physiological import is concerned: the 
lobus vagi serves as the center for a specific variety of fibres which 
mediate visceral or organic functions alone. 
With regard to the morphological aspect of the hypothesis 
further investigation will be necessary for either confirmation or 
rejection. We have no definite knowledge as to the origin of 
these buds. STRONG has shown (92) that the suggestion that they 
are related to the special cutaneous organs is negatived by their 
innervation by communis components. The buds in most or all 
forms are situated chiefly in the ectodermal territory, but those on 
the body have wandered back from the head, and the central area for 
the buds is in and about the mouth. Even here many of them are 
in ectodermal area. It is possible that the buds have been derived 
from the eee or vicinity of the mouth of the ancestor of the Verte- 
brates, from which region they have spread into the mouth and 
pharynx, and over the head and body in fishes. A careful em- 
bryological investigation of this region might throw some light on 
this interesting question. 
