132 W. BALDWIN SPENCER. 
Gasserian ganglia as arising from the first as swellings of the 
third and fifth nerves respectively, which are, from the earliest 
time of their appearance, hemmed in between the first and 
second and second and third head cavities. This description 
must now be modified, as primitively these ganglia arise in 
immediate connection with the epiblast, and only come to 
occupy their previously-described position at a later stage of 
development. 
This curious origin of the ganglia of the cranial nerves points 
strongly to the conclusion that primitively they arose as 
ganglia of the sense organs of the lateral line in the 
head, and that their present position and nature must there- 
fore be regarded as a secondary, and certainly not primitive, 
condition. 
In passing, I may just notice that on this supposition an 
explanation is offered as to the origin and meaning of the two 
curious branches! which unite respectively the ganglia of the 
fifth and seventh and fifth and third cranial nerves; they may 
be regarded as the persistent parts of the lateral nerve which 
united the ganglia of the sense organs along the lateral line in 
the head, and which, separating from the skin, have come in 
the course of development to occupy a much deeper position, 
together with the ganglia, with which they preserve their 
primitive connection. 
The development (though taking place, partly at all events, 
directly from the epiblast) of the ganglia and nerves above 
given, varies considerably and in very important points from 
that given by His for the chick. 
According to this investigator’ the ganglia are developed 
from an “intermediate cord” (Zwichenstrang), which is de- 
veloped out of the floor of an “intermediate groove” 
(Zwichenrinne), which is itself derived from the epiblast, and 
not from the neural folds whilst these are closing over. 
‘Quart. Journ. Mic. Sci.,’ Jan. 1, 1881; also Marshall and Spencer, “ Obser- 
vations on Cranial Nerves of Scyllium,” ‘Quart. Journ. Mic. Sci.,’ July, 1881. 
1 See Marshall and Spencer, op. cit., July, 1881, fig. 10, We’ and Ne. 
? «Arch, fiir Anat. und Phys.,’ 1879. 
