and the Elements in which they live. 387 
Fishes? A minute investigation of the details of this numerous 
class might lead to very interesting comparisons which however 
would be out of the way in this general sketch. 
_ Ishall mention only a few facts to show that these comparisons 
might even be traced between the different stages of growth of 
* these animals. It must be, for instance, a matter of surprise to 
see that the body of so many Insects is smaller in their perfect 
state of development than as a pupa; and that again this is 
smaller than that of the larva, thongh the larva be after all only 
the younger state of the pupa, and the pupa the younger state of 
the perfect Insect. But in the same ratio as we find so frequently 
throughout the animal kingdom that the lower condition of struc- 
ture and development of a type is manifested in a more bulky 
body, so we find among Insects, that their earlier state of met- 
amorphosis which is developed under inferior circumstances, 
teaches its final growth in a more bulky body than that of follow- 
ing periods during which their successive moultings and the trans- 
formations of the substance of the body takes place; the greatest 
size which the larva acquires is first reduced in its transition into 
a chrysalis, and this. again is reduced in its transition into a per- 
fect Insect,—the development of wings only leaving them seem- 
ingly of greater size when their surface is extended, though 
the bulk as a whole be reduced. Weighing these animals in 
these different states of development will satisfy the most incred- 
ulous of the reality of what is here stated, should the appearance 
have deceived him before. A Sill Worm when it begipe to spin is 
much heavier than the chrysalis, and this heavier than the perfect 
Without directly weighing these animals, we might 
Satisfied about this fact if we should consider the amount of silk 
Which is thrown out by the latter, and the amount of fluid which 
1s discharged by the Moth even before it rids itself of its load 
of eggs and sperm, to enjoy the last moments of its complete 
maturity. | : en Fats 
If we now allude to the Vertebrata we shall find very similar 
facts, and perhaps in the animals to be mentioned, inducements 
for the discovery of‘ curious unnoticed connections. And here 
again we should be cautious for reasons alluded to already above, 
Not to take the classes ‘as such, but rather to consider their differ- 
€nt types separately ; for the class of Fishes as a whole cannot be 
Said to contain the largest Vertebrates, nor even to afford any 
Support to the view that aquatic animals in general are larger than 
terrestrial, for we find proportionably a much greater number of 
tge species among Mammalia than among Fishes; we find a 
peer number of large terrestrial Reptiles than of aquatic ones. 
ut if we review the classes separately, and consider their second- 
ary groups by themselves, we find that the rule holds good, but 
bears, at the same time, most interesting reference to the order of 
re 
