MORPHOLOGICAL STUDIES. 
181 
of the formation of nerves is one on which, along with most 
observers, I am completely at variance with His (Nos. 29 and 
34) and Kolliker 1 (Nos. 42 and 44) ; and I refer the reader to 
a fuller discussion of it in another part of this paper. 
With this I close my account of the very earliest stages of 
the cranial ganglia in Elasmobranchii. The mode of develop- 
ment here described from at least two sources is characteristic 
for the ganglia of all the branchial nerves, facial, glossopha- 
ryngeus and vagus (fig. 24), and also for the trigeminus. 
Mutatis mutandis it also holds for the olfactory (figs. 19, 
20), mesocephalic, and auditory (figs. 25, 29) ganglia. Here 
I will only emphasize this point, reserving to myself the 
right to return to it on a subsequent occasion. To go further 
into the matter here would lead to the discussion of a great 
many disputed points, and for the moment I wish to lay more 
stress on the absolute facts of the development which can be 
demonstrated. The conclusions which I feel entitled to draw 
from those facts can for the moment be postponed. 
II. The Peripheral Nervous System of the Chick. 
Our knowledge of the development of the peripheral 
nervous system in Birds is almost entirely due to His 
(No. 29), Marshall (No. 46), and Onodi (No. 51). Kastschenko 
(No. 40) has also contributed his item, which, so far as 
nerves or ganglia are concerned, is of no particular value, 
for it contains no new facts and throws no new light on 
the morphology of either cranial or spinal nerves and 
ganglia. 
For many reasons I was obliged to include the Chick in the 
sphere of my observations. For one thing His’s remarkable 
observations and hypotheses were mainly established for this 
animal (Nos. 28, 31), and I could not feel satisfied until the 
explanation of His’s Zwischenstrang was got at the bottom of. 
The striking manner in which the epiblastic origin of the 
1 Kdlliker lias upheld his views in several papers. 
VOL. XXIX, PART 2. NEW SER. 
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