182 
MR, W. K. PARKER OK THE STRUCTURE AND 
Plate. 
Fig. 
Stage. 
Humber 
of times 
magnified. 
14 
1 
2 
Larva of Acipenser ruthenus , millims. long; 
vertical section of head. 
26 
» 
2 
3 
Second horizontal section of larva of same, 13^ 
millims. long (see Plate 13, fig. 10). 
40 
33 
3 
3 
Third section of same head. 
40 
33 
4 
3 
Same head; basis cranii, upper view. 
20 
» 
5 
3 
Same dissection as last; lower view. 
20 
33 
6 
3 
Maxillary and dentary of same dissection; side 
view. 
53 
)> 
7 
3 
First of a series of sections of the largest larva of 
Acipenser ruthenus, 14^ millims. long . . . . 
30 
>) 
8 
3 
Second section of same. 
30 
>> 
9 
3 
Third section of same. 
30 
33 
10 
3 
Fourth section of same. 
30 
>) 
11 
3 
Fifth section of same. 
30 
>> 
12 
3 
Sixth section of same. 
30 
)> 
13 
3 
Seventh section of same. 
30 
}> 
14 
3 
Eighth section of same. 
30 
15 
1 
3 
(Same sections as on last Plate, continued.) Ninth 
section of same. 
30 
j> 
2 
3 
Tenth section of same. 
30 
)) 
3 
3 
Eleventh section of same. 
30 
33 
4 
3 
T welfth section of same. 
30 
>9 
5 
3 
Thirteenth section of same. 
30 
33 
6 
3 
Fourteenth section of same. 
30 
33 
7 
3 
Fifteenth section of same. 
30 
>> 
8 
3 
Sixteenth section of same. 
30 
>> 
9 
3 
Seventeenth section of same. 
30 
99 
10 
4 
Head of a young specimen of Acipenser sturio , 
8 inches long; side view. 
u 
33 
11 
4 
The same; upper view.. 
1* 
99 
12 
4 
The same; lower view. 
1* 
