45(5 
MR. W. K. PARKER OK THE SKELETON 
Plate. 
Pig. 
Number of 
times 
magnified. 
24 
1 
Petromyzon planeri (embryo, 9'5 millims. long); first 
of a series of vertically-transverse sections of cephalic 
and branchial regions . 
150 
55 
lA 
Part of a similar section of an embryo 7*8 millims. 
long . . . 
300 
55 
2 
Second section of larger embryo . 
150 
55 
2a 
A similar section of smaller embryo . 
300 
55 
3 
Third section of larger embryo ........ 
150 
55 
4 
The same ; fourth section ... 
150 
55 
5 
The same ; fifth section. 
150 
55 
6 
The same ; sixth section. . 
150 
55 
7 
The same ; seventh section .. 
150 
55 
8 
The same ; eighth section .. 
150 
55 
9 
The same ; ninth section . . 
150 
25 
(Partly as in last Plate.) 
55 
1 
Part of the same section as in Plate 24, fig. 5. 
300 
55 
2 
Another partial section from the same series between 
figs. 5 and 6 of Plate 24 . 
300 
55 
3 
Another partial section between figs. 7 and 8 of 
Plate 24 . 
300 
55 
4 
A similar section near fig. 9, Plate 24 . 
300 
55 
5 
Same series ; a complete section through branchial 
region and thyroid body . 
150 
55 
6 
Part of last section ............ 
300 
5 ? 
7 
Skull of smaller embryo (7'8 millims. long) of P. 
planeri ; lower view. 
150 
55 
8 
Petromyzon fluviatilis (larva, 6 inches long) ; dissection 
of branchial region ; side view. 
5 
55 
9 
Part of same ; lower view. 
5 
55 
10 
The same ; vertical solid section of head and branchial 
region. 
5 
