26 

the hippocampuses, but the one is organised for flexi- 
bility and the other for very limited power of vary- 
ing the horizontality of the column. I see nothing 
of aquatic life capable of being looked into, within 
the narrow space of a basin, more interesting than 
the pair of hippocampuses brought to me. ‘They 
illustrate movement by the action of the vertebral 
column, almost to the exclusion of every accessory 
aid peculiar to fishes. 
Fishes are the lowest of the vertebrata. We have 
seen, in the extract I have made from Professor 
Grant’s comparative Anatomy, that they represent in 
the excessive development of the anterior limbs, the 
embryotic peculiarities of the quadruped. The sus 
peradded appendages to the vertebral column being 
employed in different animals for varied and dis- 
tinct purposes, are many of them wanting in given 
orders and genera. We might expect that fishes, 
from their low position in the vertebrate series, would 
present some remarkable evidences of the deficien- 
cies of the accessory composition, and the indepen~- 
dent power of the central axis; and so they do. 
The adapiation of the spinal column for flexibility 
without any versatile appendages will be most inter- 
estingly seen in the hippocampus or sea-horse.— . 
There is a dorsal fin, but it is very subordinate in. 
its functions: there isan anal fin, exceedingly rudi- 
mentary but found only in one sex, the female. 
There is besides all this sexual peculiarity in these 
fishes, which reverses the economy of gestation , 
The male have a pouch into which the female injects 
the oya, The eggs are fertilized by impregnation 

