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cells. Comparing these results with my own recent researches!) there is 
perhaps more of agreement — at any rate in the observed facts — 
than of dissension. 
My standpoint is not entirely new. I have long upheld the doctrine 
that nerves arose from chains of epiblastic cells, but only within the 
last year or so has what I take to be the actual mode of nerve for- 
mation from such chains gradually forced itself upon me. In the inter- 
pretation of the facts our agreement is not so clear. For my part 
the help derived from the recent work of my colleague, Dr. Berry 
HAYcRAFT , must be admitted. Last year this gentleman asked the 
use of my preparations of Vertebrate embryos for his researches on 
muscle. Naturally I had no objections; my sections have always been 
at the service of fellow-workers. 
I was much interested in HAycrart’s investigations, and soon 
perceived that his results promised to be of importance. In two senses 
his work was before me in my own studies; for I had constantly under 
examination preparations (showing muscle development), which we had 
often looked at together, and his views on various histogenetic pro- 
blems were ever in my mind. Muscle and nerve, cells and the cell- 
theory have been the themes of many conversations and discussions 
between us during the past summer and winter, and the combination 
thus formed of a physiologist and histologist with an embryologist has, 
I venture to think, been one, which, in these days of specialisation, 
could not be without its advantages to both. At any rate, speaking 
for myself, I have to acknowledge what I owe to Haycrarr in the elu- 
cidation of many of the problems of my researches. 
In its essentials I find, as Haycrarr suspected, nerve develop- 
ment to bear some resemblance to the histogenesis of muscle ?), for 
nerve cells secrete nerve fibrils and an inter-fibrillar substance known 
as the white substance of SCHWANN. 
1) Vide “The nose and Jacosson’s organ’, Zool. Jahrbücher, Anat. 
Abteil., Bd. III, p. 759. “Most nerves in the Vertebrata are trans- 
formations of ganglion cells”. The reader will find “‘nerve-chains” spoken 
of in various passages of this and others of my papers. 
2) The recognition of this similarity is some 50 years old, and was 
especially noted by VaLENTIN in a memoir which, but for the influence 
upon it of ScHLEIDEn’s work on the tissues of plants, would have antici- 
pated much that is here written of nerve-histogenesis. Considering the 
epoch of its appearance VaLENTIN’s work may well be styled remarkable. 
On another occasion VALENTIN’s services in this direction may, it is hoped, 
be done justice to. The memoir “Zur Entwickelung der Gewebe des 
Muskel-, des Blutgefäß- und des Nervensystems, von G. VALENTIN” is to 
be found in Mürrer’s classic “Archiv” 1840. 
