REVIEW. 139 
can be said of it is, that it does not contradict the view. Inspite 
of his evident candour, the author has not always resisted the 
temptation of straining his points to the uttermost limit, often 
preferring a. far-fetched and doubtful explanation to an obvious 
one close at hand, as in the case of the zebra and niata hybirds, 
on p.130. The statement that the peculiarities of the niata 
breed ot Paraguay cattle are probably due to a reversion to the 
type of Sivatherium will be an amusing one to paleontologists. 
Then it is not at all clear from the evidence presented, that 
this hypothesis will account more satisfactorily for the greater 
development of the male in those species in which the sexes 
differ than does Darwin’s theory of sexual selection: for admit- 
ting Professor Brooks’s doctrine, that each individual inherits a// 
the characteristics of the species, and that the female function 
prevents the development of the male characters (though they 
may appear when that function is destroyed), it is plain that those 
characters are either incompatible with the female function or use- 
less to the female, and hence there is no reason why she should 
acquire them ; while their presence in the male, to which they 
are of obvious advantage, is in most cases to be accounted for by 
sexual selection. On the other hand, it is obvious that all the 
complex apparatus of uterus, placenta, and similar organs must 
have originated with the female. Wecannot agree with Pro- 
fessor Brooks, that the presence of mamme in the male is an in- 
dication that the mammary function was originally a male 
characteristic, any more than that the presence of rudimentary 
stridulating organs in female Orthoptera shows that these were 
first acquired by the female. Why should Professor Brooks 
adopt exactly opposite explanations for exactly parallel cases ? 
Propagation of cells by means of gemmules is not only purely 
hypothetical, but, apparently at least, opposed to what we know 
of the mode of cell-formation. Cells arise only by division of 
some pre-existing cell, and never seem to arise spontaneously, 
as would very probably be the case it their propagation by gem- 
mules were at all common. Nor does the process of impregna- 
tion, as actually observed, lend support to the new .hypothesis ; 
for the head of the spermatozoon coalesces with the nucleus of 
the ovum, apparently without loss of bulk, ’or in any way indi- 
cating an emission of gemmules. The influence of the male ele- 
ment seems rather to consist in modifying the action of the egg- 
nucleus. 
Mr. Conn’s very obvious objection (given on p. 294), that in 
many cases unfavourable conditions would not act upon certain 
cells, causing them to emit gemmules, but would result in the de- 
struction of the animal, seems entitled to more weight than the 
author is inclined to give it. Any hypothesis that fails to account 
- so large and important a class of facts cannot be called com- 
plete. 
Want of space compels the omission of many other objec- 
tions, as well as the considerations of Professor Brooks’s views 
on reversion, natural selection, and the intellectual differences 
