MORPHOLOGICAL STUDIES. 
177 
to give a very detailed account of such formation in individual 
cases. From Professor Gegenbaur one must apparently be 
thankful for small mercies, and as this is the one thing in 
my researches which he admits unreservedly that I have seen, 
I quote his testimony in my favour. He says (No. 21, p. 41), 
“ Die Beziehung des Ganglions zu dem Ektoderm ist von 
Beard richtig erkannt worden : er sagt, ‘The proliferated cells 
form a mass of actively dividing elements still connected with 
the skin and fused with the dorsal root; for some 
time the cells continue to be given off, and of those already 
given off many show nuclear figures/ Die epitheliale Ver- 
dickung hat also die Bedeutung einer Quelle der Ganglien- 
bildung. Das geht auch aus den beziiglichen Figuren Beard’s 
hervor, die zudem in der Anordnung der Elemente der 
am Ganglion befindlichen Ektodermschichte gar 
nichts aufweisen, was man auf ein liier sich bil- 
dendes Sinnesorgan beziehen konnte. Wenn die That- 
sachen, wie sie in Wirklichkeit bestehen, die Grundlage der 
Forschung abgeben, so kann man hier nur sageu ; der Nerv 
wachst vom Centralorgane aus unter dem Ektoderm bis zu 
einer Stelle, an der ihm aus dem Ektoderm ein Zufluss von 
Formelementen zu Theil wird.” 
For the present moment I leave entirely alone Professor 
Gegenbaur’s doubts about the sense organs. Such doubts are 
entirely unjustifiable. To return to the ganglionic Anlagen 
derived from the epiblast at the neural side of the head. 
These Anlagen grow outwards and downwards towards the 
lateral surface of the body. Just above the gill-cleft there 
is here a small portion of neuro-epithelium (figs. 94, 95), 
which is the Anlage of the branchial sense organs or lateral 
sense organs. This neuro-epithelium has begun to extend its 
growth before the ganglionic Aulage fuses with it. 1 In figs. 
94, a and 95, a, 1 have represented this. The growth has 
1 Fig. 101 shows this growth for the auditory epithelium of a lizard. Just 
as all the lateral sense-organs are formed from a certain limited number of 
pieces of neuro-epithelium, so all the sensory cells of the ear arise from the 
extension of one little bit of neuro-epithelium ( o . e.) 
