1899] A COMPLEMENTARY MALE 15 
found a careful student in Mr. A. Gruvel (Arch. Biol. xvi. 1899, pp. 
27-47, 1 pl.). In Hoek’s Challenger Report there is some account of 
the complementary male of Sc. regiwm, which is said to have two ganglia, 
a functionless stomach, and cement glands, but not much else. In the 
species studied by Gruvel the male is also very simple. It has two 
ganglia and an eye, but no digestive canal nor specialised vascular and 
respiratory apparatus. It is little more than an independent testicle 
endowed with a minimum of individuality. 
Mr. Gruvel finds it difficult to admit that similar eggs fertilised by 
spermatozoa of the same origin produce larvae destined to give rise, 
some to hermaphrodites and others to these pigmy males. And so he 
has thought out a theory which may render the affair less mysterious, 
though we are not at all confident that it does. Cirripeds are usually 
protandrous, z.e. the spermatozoa ripen before the ova. The sperms are 
shed first, and accumulate in the interpallial space. By and by the ova 
pass into the ovigerous sac, and are there fertilised; as they develop, 
the gaps in the sac are closed, and the whole is detached from the 
genital atrium to be fixed to the ovigerous frenum. Thereafter there 
emerge belated ova which have a poor chance of being fertilised by the 
spermatozoa of the hermaphrodite. And Gruvel’s theory is that these 
are fertilised by the spermatozoa of the complementary male, which are 
usually longer of developing than those of its bearer, and that from 
these ova thus fertilised complementary males are produced. 
Is Fertility Inherited ? 
In the sixth of his valuable memoirs entitled “ Mathematical Contribu- 
tions to the Theory of Evolution,” Prof. Karl Pearson, with the assist- 
ance of Miss Alice Lee and Mr. Leslie Bramley-Moore, brings forward 
evidence to show that fertility is inherited in man, and fecundity in the 
horse, “and therefore probably that both these characters are inherited 
in all types of life ”—in all likelihood according to the Galtonian rule. 
We have only seen the abstract in the Proceedings of the Royal Society 
(ixiv. 1899, pp. 163-167), but that is enough to show the interest and 
importance of this inquiry, especially in connection with “reproductive 
or genetic selection ”—a term (which seems to us unfortunate) used to 
describe “the selection of predominant types owing to the different 
grades of reproductivity being inherited, and without the influence of a 
differential death-rate.” 
Mr. Pearson points out that the problem of whether fertility is or 
is not inherited is one of very far-reaching consequences. “The 
inheritance of fertility and the correlation of fertility with other 
characters are principles momentous in their results for our concep- 
tions of evolution; they mark a continual tendency in a race to 
