i88o.] 
Analyses of Books. 
203 
ordinary fadl. Among the Hymenoptera numerous species of 
Cynips have, according to the author, no known males. Dzierzon 
has detedled parthenogenesis in the hive-bee. Even among 
vertebrate animals unfecundated ova undergo a partial develop 
ment. The segmentation of such ova was observed by Bischoff 
in the frog, the bitch, and the sow, and these observations have 
been verified by more recent authors. Agassiz and Burnett re- 
cognised evident traces of segmentation in certain American 
species of Gadus. In the common hen, Oellacher discovered 
that the non-fecundated eggs experience a beginning of segmen- 
tation in the ovidudl. But there is no known instance among 
vertebrate animals of the development having proceeded to the 
formation of a perfedt animal. 
It must be admitted, in the meantime, that this explanation of 
parthenogenesis raises a number of further questions. Thus the 
last generation of Aphides produced every season is composed 
of individuals of both sexes. Yet, in a heated conservatory, 
Aphis rosce has continued to reproduce itself by parthenogenesis 
for four years in succession. Why is this ? Why, among these 
insedts, are the individuals produced by parthenogenesis brought 
into the world living, whilst those normally generated appear 
as eggs ? 
Concerning the spermatozooids, Professor Balbiani does not 
unhesitatingly admit the modern theory, which regards them as 
mere histological elements, analogous to the blood-corpuscules. 
He considers that there is something to be said for the old 
dodtrine of their vitality. He holds that their movements display 
a certain degree of purpose, being diredted to a definite end. 
Thus in Bombyx mori at the moment of intercourse the seminal 
fluid of the male is received in a special vesicle, which the next 
day is found completely empty, all the spermatozooids having 
emigrated into another capsule, which opens into the ovidudl: 
opposite to the former capsule, and where they await the ova , to 
fecundate them in passing. But the walls of the former recep- 
tacle have no contradlile elements, so that the passage of the 
spermatozooids from one capsule to another can only be due to 
a spontaneous inward movement. In the former receptacle 
there remain only a few misformed and motionless spermato- 
zooids. There exists consequently a kind of “ natural selection,” 
even among the sexual elements. 
On the Nature of Life : An Introductory Chapter to Pathology. 
By Ralph Richardson, M.A. Second Edition. London : 
H. K. Lewis. 
We have here an exposition and a criticism of the three preva- 
lent theories of life, the so-called physical, the vital, and the 
