Panmixia and the Principle of Economy 1g! 
The addition suggested by Romanes that the tendency 
to atavistic reversion favors minus variations at the 
expense of plus variations, does not suffice! For in 
the first place an atavistic reversion could appear at best 
only in the phyletic characters acquired last, and in the 
second place, after the first stages of atrophy had ap- 
peared it would in any case tend from that time on to 
insure the preponderance of plus over minus variations. 
One could nevertheless assert that panmixia is not 
necessary for Weismann’s theory. The principle of the 
economy of the organism by which every useless and 
unused organ is harmful because it withdraws nourish- 
ment from other organs is by itself enough, if one 
rejects the inheritance of acquired characters, to explain 
the gradual phyletic disappearance of useless parts. 
But this hypothesis is easily refuted by some calcula- 
tions of Spencer, showing that it is impossible that the 
advantage to the organism of a small inborn and fortu- 
itous minus variation in the useless organ, particularly 
when this is already very much degenerated as is for 
instance the hind leg of the whale, can procure for the 
individual an advantage over others and so provoke the 
phylogenetic passage to a yet greater atrophy. And no 
great value can be attributed to the counter observation, 
which Weismann several times repeats, that we are still 
quite unable to measure the selective efficacy of the 
struggle for existence. One need think only of the 
parasites and particularly of the endoparasites, which 
have always an excess of nutrition and in which there- 
fore the advantage of the degeneration of useless organs 
would become reduced absolutely to zero. And it is 
181Romanes: A Note on Panmixia. Contemporary Review. Octo- 
ber 1893. P. 612. 
