1890.] Recent Literature. 753 
Prof. Eimer takes occasion frequently to criticise the opinions of 
Prof. Weismann. The following is a sample of this polemic : 
* In the paper previously mentioned, * Retrogression in Nature,’ . 
Weismann replies with greater detail and precision than on previous 
occasions to the objections which may be made—as they have been 
made by me—to his theory on account of the facts of the degeneration 
of organs in consequence of disuse. 
* Starting from the proposition that *the adaptation of living 
beings, in all their parts, depends on the process of natural selection,’ 
he infers that this adaptation must be maintained by the same means 
by which it was produced, and that it must again disappear as soon 
as this means, natural selection, fails to act. 
* In other words, he says: Through natural selection alone forms 
have come to be what they are. By the continuation of natural selec- 
tion only are they maintained in their present state. If selection 
ceases, they of necessity retrograde. But selection with respect to a 
particular organ obviously ceases as soon as that organ is no longer 
necessary (*the reverse side of natural selection' ); its cessation, 
therefore, produces the degeneration of organs. 
“It is, according to my view, self-evident that the cessation of 
natural selection can as little cause the retrogression of an organ as 
natural selection can cause it to develop. Selection is, I must ever 
repeat, no physiological factor which could produce any thing new, 
or whose cessation could annul anything existing. Organs are pro- 
duced by external stimuli, or by use acting upon the material given in 
a given case, with the aid of general and of sexual selection." 
In this position the author is in entire harmony with the views of 
the Neo-Lamarkian school in America and England ; and he supports 
it with an array of facts which fill a great part of the 435 pages 
which comprise the volume. We regret that he has not been appar- 
ently acquainted with the opinions entertained by his co-workers on 
this side of the Atlantic, as he might have derived some facts of use 
to him. To paleontology, that mine of evidence for the evolutionist, 
he makes but little reference ; and, in fact, this subject has not been: 
within the scope of his researches, which have been so abundant in 
other directions. 
With respect to the cause of variations, he adduces the following 
example : | 
«Oscar Schmidt points out further that numerous [other] cases in 
sponges have been described by Haeckel and himself, in which the 
| organisms are beginning to change into new species by the disappear- 
