124 
MR. W. K. PARKER OK THE STRUCTURE ARD 
The following are the stages worked out in Erinaceus europceus :— 
First Stage. Embryo of Erinaceus europceus , about two-thirds ripe ; inch 
long.* 
Second Stage. The same species, about three-fourths ripe ; 2| inches long. 
Third Stage. New-born young of the same species ; inches long. 
Fourth Stage. Young Hedgehog, two weeks old, or thereabouts; 3 inches 
long 1 . 
Fifth Stage. Young Hedgehog, about a month old ; head 1^ inch long. 
Sixth Stage. Young Hedgehog, two-thirds grown. 
Seventh Stage. Young Hedgehog of first winter. 
Eighth Stage. Adult Hedgehog, nearly, or recently—not old. 
First Stage of Erinaceus europseus; embryo two-thirds ripe; lj inch long. 
(Plate 17, figs. 1, 2.) 
In this solid little embryo, with the “ panniculus ” formed, the prickles beginning 
to project (Plate 16, figs. 8, 9), the chondrocranium (Plate 17, figs. 1, 2), is no longer 
pure cartilage.! 
a. Dissected endocranium. 
The floor and sides of this skull-barge are well formed, except that large cracks or 
fissures show themselves below ; it is almost as fully formed of cartilage as that of a 
young Skate of the same size, but shows some very remarkable modifications that are 
diagnostic of the Mammal. For instance, the nasal capsule runs along the whole 
extent of the rostrum, or intertrabecula. The sides of the barge-like structure have 
given way, right and left between the ear and the eye, or between the auditory capsule 
and the orbitosphenoid (o.s.); thus the alisphenoids are squeezed, as it w’ere, outside 
the rest of the structure, as if part of a wall should bulge out and break away from 
the “ coping-stone.” 
To those two characteristics I may add the extensive plate of perforated cartilage 
(“ cribriform plate ”) for the multitudinous nerves proceeding from the “ rhinen- 
ccphala.”! 
This irregularly pyriform chondrocranium is a very extensive and complex structure, 
through the union, with the cranium, proper, of the fore and hind sense-capsules. 
* In all the measurements I exclude the tail, unless it is specially mentionedthe length is from the 
snout to the root of the tail, the length of the head and body, separately measured, being added together. 
f In my next instance—the Mole—I shall give an account of that earlier stage, before any bony 
deposit has appeared. (See Plate 25, figs. I, 2.) 
+ The only other type that shows a cribriform plate is the Myxinoid (see Phil. Trans., Yol. 174, 
Plate 17, fig. 4, p. 401) ; in that case, however, only jive nerves pass out on each side, through a 
perforated membrane. 
