42 J. DB. Johnston. 
nervous structures. The origin of certain visceral plexuses in man 
and of various peripheral nerve cells in other vertebrates has not 
been determined, and the origin of taste buds is at present under 
discussion. The statement that all nervous structures are derived 
from the ectodermal layer of the embryo is not warranted by the 
known facts. Another reason for thinking that taste buds are of 
ectodermal origin is that in certain fishes they are found in the later 
embryo and adult in ectodermal territory, namely, the outer skin. 
In 1898 I made the statement that in the head of vertebrates ‘all 
sensory structures of ectodermal origin are supplied by components 
of the Vth (including spinal Vth components running in other 
nerves), VIIIth and lateral line nerves, and that all fibres supply- 
ing such structures have their central endings in the nucleus funiculi, 
tuberculum acusticum or cerebellum. . . . On the other hand, all 
sensory structures of entodermal origin are supphed by VIIth, I Xth 
and Xth components, and all fibers supplying such structures have 
their central endings in the lobus vagi.” 
The inclusion of taste buds among structures of entodermal origin 
was adversely criticised by Strong (1898), and it did not appear 
that any neurologist was ready to entertain the idea that taste buds 
were possibly of entodermal origin. I have since brought forward 
evidence (1905) that in petromyzonts the taste buds arise in ento- 
dermal area. In the ammoceetes stage I was able to find them only 
in entodermal surfaces. In teleosts (Coregonus, Catostomus) the 
buds first appear in the pharynx and cesophagus where there seems 
to be no possibility of origin from any other source than entoderm. 
The appearance of taste buds in entodermal area in teleosts has since 
been confirmed by Landacre (1907), working on Ameiurus. He 
recognized, however, the possibility of their being formed in ectoderm 
also. 
Marrriat and Mrrnops. 
I have undertaken to study the limits of ectoderm and entoderm 
in the mouth of several vertebrates, both for its general interest and 
with especial reference to the origin of taste buds. 
Amphibians offer especial advantages for the study of the relations 
