QUATREFAGES, ON MAN AND THE LOWER ANIMALS. 37 
infancy to puberty. This is not the case; no particular 
details of the embryology or subsequent development of the 
human species being entered upon, the scope of the author 
has been to lay before his readers the life-history of the 
animal kingdom in general. Most of the chapters here intro- 
duced appeared originally as a series of essays in the ‘ Revue 
des Deux Mondes.’ These articles are here reprinted together 
with an account of the progress made since their first appear- 
ance. “Its origin,’ says the author, “ will explain the 
character of the book. In the original articles, I avoided 
being very technical, merely giving accurate views , Supported 
by the most striking illustrations. In the present volume Iam 
forced to preserve this feature, unless I were to produce a 
completely new work. Such as it is, I trust that this treatise 
may be accessible to all who are accustomed to serious reading. 
At the same time, it will present to naturalists, the principal 
facts with which they are acquainted, arranged in a manner 
peculiarly my own and with reference to several works 
scattered here and there. Perhaps in these different aspects 
it may prove of service. Such at all events is the object with 
which I published it.” 7 We feel persuaded, from a perusal of 
the work, that the author has fully accomplished that object. 
The first chapter of the volume is devoted to an explana- 
tion of the necessity for reproduction, of the waste and re- 
newal of matter continually taking place in animals, resulting 
finally in death. The next chapter comprises the definition of 
the term metamorphosis. By ¢ransformation, the author means 
the series of changes which take place in the ovum, and those 
which species born in an imperfectly developed state, present 
in the course of their external life; the term metamorphosis 
is retained for the modifications undergone after exclusion from 
the egg, and which alter extensively the general form and 
mode of life of the individual: geneagenesis signifies those 
changes which relate to generations themselves, including 
therefore the phenomena known as parthenogenesis, meta- 
genesis, &c. Then follows a description of the changes or 
transformation of the ovum, the process of yelk division, the 
development of the blastoderm, the germinal area, and the 
primitive streak. This part of the subject is treated minutely, 
with many references to important papers which from their 
scattered nature might otherwise easily escape the English stu- 
dent. The cell-theory of Schwann, which at one time was so 
ardently supported in Germany is discussed by the author in 
connection with the development of the egg. Many serious 
mistakes arising from the study of the higher animals exclu- 
sively have been corrected by an investigation of the anatomy 
