160 
from all the classes of animals, especially selected among those best 
known as characteristic of (his continent; also deseriptions of a great 
number of new genera and species of Polypi, Acalephz, Echinoderms, 
Bryozoa, Aseidians, and other naked Mollusks, Worms, lower Crusta- 
ceans, and Fishes, accompanied with accurate figures, and such 
anatomical details as may contribute to illustrate (heir natural affinities 
and their internal structure. 
] shall not extend my publications to classes already illustrated - 
by others, but limit myself to. offering such additions to the Natural 
History of the States I have visited as may constitute real contributions 
to the advancement of our knowledge. 
From a careful estimate of the materials I have now on hand, 
I ma satisfied J shall be able to include the most valuable part 
of my investigations in ten quarto volumes; each volume con- 
taining about three hundred pages, with at least twenty plates. 
Each volume shall be complete in itself, containing one or several 
independent monographs; so that, if any unforeseen difficulties 
published shall not remain imperfeet. As far as possible, I sha 
always select first such of my papers as contain {he largest amount 
of wew matter, or as may contribute most directly to the advan- 
cement of science. Having devoted the greatest part of my time“ 
to the investigation of the embryonie growth of our animals, I shall 
make a beginning with the embryology of our turtles, several of whi 
I have traced through all their changes; and next proceed to a 
illustration of the highly complicated phenomena of alternate generation 
budding and metamorphoses of our Hydroids, many of which I have 
followed, for many years, in all their transformations, in the open 
sea äs well äs in confinement. I trust these monographs will affo 
our medical students a fair opportunity of making themselves fam 
with the modern results of one branch of physiology, which has the 
most direct bearing upon tbeir seience, and for which the different 
species of the family of turtles found in every part of the United State 
will afford them a better opportunity even than the artificial breedin; 
of hens’.eggs. Moreover, the extent of my embryological researches 
covering, as Ihey do, all the elasses of the animal kingdom, 'w 
furnish, I trust, a new foundation for a better appreciation of th 
the possibility, upon this basis, of determining, with considerable p 
eision, the relative rank of all the orders of every class of animals 
and of furnishing a more reliable standard of comparison between the 
extinet types of past geological ages and the animals now living upon 
earth. On the other hand, my monographs of our Polypi, Acalepha | 
