178 
J. BEARD. 
already extended behind the gill-cleft (fig. 95, 5), and also 
in front of the gill-cleft (fig. 94, a). In connection with 
the morphology of nose and ear this point is one of con- 
siderable importance, and I shall have occasion to refer 
to it again. The ganglionic Anlage now fuses with neuro- 
epithelium at one point. At the point of fusion a prolifera- 
tion of the cells of the neuro-epithelium takes place into the 
ganglionic Anlage. The proliferated cells form a mass of 
actively dividing elements still connected with the skin, and 
fused with the rest of the ganglionic Anlage. Externally to 
this thickening is situate what Professor Eroriep (No. 17) and 
I regard as the primitive branchial sense organ of this segment. 
Here again I refrain from discussing any of the questions con- 
nected with the formation and morphology of these sense 
organs. 
One fact at least holds as the result of this skin fusion, and 
this is that a number of form-elements are given off into the 
ganglion. The recognition of this fact does not come to me 
after reading Professor Gegenbaur’s paper quoted above. I 
had long before seeing that written as a note, on p. 21 of my 
paper (No. 8), on the “ Old Mouth and the New/’ “The 
cranial ganglia of Vertebrates are far more complicated mor- 
phologically than has hitherto been recognised. In addition 
to parts which appear to correspond morphologically to the 
posterior root ganglia of the spinal nerves plus the sym- 
pathetic ganglia, they also contain the special ganglia which 
are formed in connection with the gill sense organs.” 
The ganglion complex soon begins to leave the skin, 
and in doing so a number of cellular fibrous cords are left 
behind connecting the sensory epithelium with the ganglion 
complex. 
The sensory epithelium has, briefly stated, usually grown 
in three directions in front of the gill-cleft, behind the gill- 
cleft, and above the gill-cleft, either in a neural, or a forward, 
or a backward direction. The nerves connecting these various 
sensory elements with the ganglion appear to me to be all 
derived as splittings off from the inner layer of the sensory epi- 
