162 
J. BEARD. 
hypothetical views on this matter. That the Zwischenstrang 
has any concern in the formation of the ganglia is a baseless 
assumption. 
In his ‘ Lehrbuch der Entwickelungsgeschichte,’ &c., Ed. ii, 
Professor O. Hertwig has made an attempt to extract a little 
light from the chaos which reigns over our knowledge of the 
development of the peripheral nervous system. For Professor 
Hertwig, the most important researches are those made by his 
pupils and by Sagemehl. As he mainly relies upon these and 
ignores for all practical purposes almost entirely the more 
recent work on the matter, it is not unnatural that the chapter 
on the peripheral nervous system is one of the most unsatis- 
factory in the whole work. As an instance of Professor 
Hertwig’s treatment of recent authors, I may mention that for 
him our knowledge of the formation of the lateral nerve of 
Amphibians and Silachians is confined to the older observa- 
tions of Semper and Goette, and he only mentions incidentally 
that van Wijhe has seen similar fusions of epiblast and sensory 
nerves in the head of Elasmobranchs (No. 23, p. 338). 
Professor Hertwig has thought fit to illustrate his account 
with one or two figures from as yet unpublished researches of 
Professor Rabl. If Professor Rabl is to pose as an authority 
on the formation of spinal ganglia, one may at least ask for 
tolerably correct figures in illustration of his work. The two 
figures 175 and 171 given by Hertwig are among the most 
incorrect that have been published till now on this matter. 
As the climax to Professor Hertwig’s appreciation of work on 
the peripheral nervous system, let me add that he is of 
opinion that “ um auf dem schwierigen Gebiete vorwarts 
zu kommen, muss man bei der Untersuchung 
von Embrvonen nicht nur Schnittserien, sondern auch andere 
histologische Methoden zu Rathe ziehen” (p. 337). It is to 
be hoped that besides giving the advice Professor Hertwig 
will also show us the way to use his “andere histologische 
Methoden.” From these citations the reader will, I think, 
be convinced that from the researches till now published, 
we may form very different conceptions of the results 
