373 
REYIEWS. 
COMPARATIVE PHYSIOLOGY.* 
T HE accomplished author of the Souvenirs d’un Naturalistc has pro- 
duced under this title a very readable little book, which treats of 
one of the most complicated questions in physiology — that, namely, 
which has reference to the extraordinary variety of forms derivable from 
the same species among some of the lower animals, their mutual relation, 
and the analogies which may be discovered between them and some of 
the phenomena exhibited in the reproductive processes of the higher 
animals. There are few questions in the range of physiological inquiry 
which have raised greater feelings of wonder, or which have given rise 
to more speculation than those which have received the name of 
“ alternate generation,” “ parthenogenesis,” &c., while at the same 
time the obscurity and complexity of many of the phenomena have 
stimulated the curiosity of some, and deterred other investigators from 
entering upon a subject of so much difficulty. 
M. de Quatrefages commences his work by pointing out that change is 
inherent in animal bodies, the highest no less than the lowest — plants and 
animals are momentarily losing some of their substance, which must 
be renewed ; and this applies to all parts alike, the most delicate, and 
those which are most assimilated to inorganic bodies. He points out 
the defects in the general acceptation of the term metamorphosis , and pro- 
poses three expressions, each having a distinct meaning, to be applied to 
the very different forms of change which take place in various grades of 
the organic kingdom, viz., transformation , which includes the whole of 
the changes which a germ undergoes in its progress to the condition of an 
embryo ; metamorphosis he retains to imply the changes which the 
animal undergoes after exclusion, and which profoundly alter the general 
forms, or the modes of life of the individual ; while he proposes the new 
term geneagenesis for those changes which refer to the generations them- 
selves — a term derived from yerea, birth, and ysyeaic, generation. 
The transformations, then, which take place in the egg, or ovum, next 
occupy the attention, from the first appearance of organized tissue 
through all those remarkable stages which have of late years been so care- 
fully and elaborately worked out and watched, more particularly by 
* “ The Metamorphoses of Man and of Animals,” by A. de Quatre- 
fages. (Me'tamorphoses de l’Homme et des Animaux, par A. de 
Quatrefages.) Paris : J. B. Bailliere, 1862. 
