Zoology. 125 
as anatomical investigations would seem to indicate. For it is now 
plain that the spreading appendages of the body of Pteropoda are not 
analogous to the long tentacles which encircle the head in cuttle-fishes, 
but correspond to the vibratory rudders of the embryo in marine Gas- 
teropoda. 
Again, the position of Foraminifere, seems to me no longer doubtful. 
They are neither microscopic Cephalopoda, nor Polypi, as of late it 
has been generally thought best to consider them, but constitute a truly 
embryonic type in the great division of Gasteropoda, exemplifying, in 
this natural division, in a permanent condition, the embryonic state o 
development of common Gasteropoda, during which the bulk of the 
yolk passes through the process of repeated divisions. = 
is principle—of embryological changes as a foundation of the’ 
natural classification in the internal arrangement of all the minor groups 
in the natural classes of the animal kingdom—applies with equal suc- 
a comparison of the metamorphoses themselves, in the different genera, 
will leave no doubt as to which of them the highest rank should be — 
assigned 
here to add, that even the classification of mammalia will receive decided 
improvements upon the consideration of their embryological changes. 
A single instance, even now, will at least show that the true relative 
rank of their families can be determined in that way. 
t oe 
_ These remarks will, at the same time, show that no investigations: 
re at present more needed to improve our natural methods in classifi-. 
it natural uld, 
_ Contribute more to the advance of Zoology, than any amount of descrip- 
ton of new species, : ,. 
oe these investigations of young animals should be made witha full 
knowledge of their various relations, and with the view of ascertaining | 
chiefly those zoological liariti hich illustrate more full 
eis. Ze peculiarities, which may 1 ¥ 
the value of all these relations. : 
Pe cle 
fic 
