] 86 
J. BEARD. 
II, b. The Cranial Ganglia in the Chick. 
As we have seen, the development of the cranial ganglia in 
the Chick was described by Marshall (No. 46) just ten years 
ago. He says, p. 15, “ About the twenty-second hour a small 
outgrowth of cells appears along the mid-brain on each side, at 
the angle between the external epiblast and the neural canal — 
the neural ridge. This rapidly extends both forwards and 
backwards ; forwards as far as the anterior part of the optic 
vesicles ; backwards, along the whole length of the brain, and a 
certain distance down the spinal cord. Its first appearance 
precedes the closure of the neural canal.” And on p. 12 (1), 
“ The neural ridge appears before closure of the neural canal 
is effected, so that the ridges of the two sides are primitively 
independent of each other.” (2) “ The ridge is not developed 
directly from the external epiblast or from the neural canal, 
hut from the re-entering angle between the two.” 
His (No. 29) has also given some partially correct figures of 
the first origin of the cranial ganglia in the Chick (Taf. xvii, 
fig. 3, a — /). The remaining figures of the series g and h are, 
I think, not correct; and the interpretation put on the (only 
partially correct) figures by His is one which, along with 
Balfour, I cannot accept. 
His himself (No. 29, pp. 464 — 465) summarises his conclu- 
sions as follows : 
“ Ich halte dafiir, dass das Gebilde, welches ich beim 
Hiihnchen Zwisclienstrang genaunt babe, weder eine'AVuch- 
erung ’ des Medullarrohres, noch einer solclien des Horn- 
blattes seinen Ursprung verdankt, sondern einem zwischen 
diesen gelegenen besonderen Substanzstreifen. Dieser Sub- 
stanzstreifen grenzt sich schon vor Eintritt des Markschlusses 
in mehr oder minder auffalliger Weise ab und so bildet er 
eine Rhine, die von mir sogeu. Zwischenrinne. 
“Nach meiner Ansicht gliedert sich demnach das obere 
Grenzblatt oder Ectoderm in dreierlei Anlagen ; in die 
Medullarplatte, in die beiden Zwischenstrang-platten und in 
