The Cranial Nerve Components of Petromyzon. 187 
There is apparently a marked difference between the behaviour 
of the general and the special eutaneous components in the system 
of branchial nerves. This differenee might disappear if we knew 
the innervation of the organs over the gill slits. It is probable that 
both general and special eutaneous components are present in both the 
branchial nerves and the »hypoglossus« trunk. 
The Visceral Sensory System. 
The faseieulus eommunis eomponent in the VIL!" nerve is very 
small and this fact seems to indicate a sparse innervation of the 
visceral surface. But in fact this surface has been somewhat reduced 
and in the absence of special sense organs a large nerve is not to 
be expected. The communis fibers innervate only the cephalie wall 
of the first permanent gill sac. The connection of the sympathetie 
trunk direetly with the visceral component of the VII: nerve is an 
indieation of the elose relation primarily existing between the 
sympathetie and the visceral sensory nerves, and gives direet support 
to the interpretation recently given (23) of the sympathetie as an 
offshoot of the visceral nerves. It is possible that there is a similar 
eonnection with the IX '% nerve in the species described by HATSCHEK 
(11, Fig. 11). 
The faseieulus communis component in each of the branchial 
nerves innervates an extremely interesting set of sense organs. 
These organs were first described by SCHNEIDER (34) as taste organs. 
Their development was studied by DoHrN (35) who considered them 
to be glands. Other authors supported the same view. Rerzıus (36) 
independently diseovered them and described them as taste organs. 
SCHAFFER (33) has studied and figured them carefully, reviewed the 
literature regarding them and brought together the evidence that 
they are sense organs. The organs are markedly different from the 
epithelial glands in the pharynx of Petromyzon, they contain no 
gland elements but have instead two kinds of cells which are to be 
considered as sense cells and supporting cells, and they are provided 
with nerves. If we add to this the two important facts, first that 
the sense eells are the same slender rod-shaped cells extending the 
whole depth of the epithelium which characterize taste buds in all 
vertebrates, and second that tbey are innervated by fascieulus com- 
munis components which always innervate taste buds, the anatomical 
evidence for their funetion is complete. I may add that in my pre- 
parations the difference between sense cells and supporting cells is 
