560 
batis, and that of the twofold spermatozoa of Paludina and Pygaera 
suffice to demonstrate the truth of this. 
The faculty of becoming hermaphrodite is confined to the female. 
The male can only produce spermatozoa, often of two kinds, but only 
one form of functional gamete. The female produces two kinds of 
functional eggs, from one of which, the male-egg, she is able on 
occasion by anticipation to form spermatozoa. In all described cases 
of hermaphrodite (male) individuals among vertebrates the forerunners 
of a second form of sperm (spermatogonia or spermatocytes) have been 
erroneously taken to be “eggs”, 
Hermaphroditism is associated with the partial or complete sup- 
pression of one form of gamete, the male-egg; Parthenogenesis, on 
the other hand, entails the occasional, or the cyclical, arrestment of 
one or other of the two gametes of the female. If it become acyclical 
(WEISMANN) with the consequent disappearance of the males, with 
these there vanish the male-eggs, which produce them, and the sper- 
matozoa. In such instances the only form of gamete left is the female- 
egg, which, as is well known, undergoes an isogamous union with a 
rudimentary sister, the polar body. 
Of very great importance for many questions is the recognition, 
that any particular form of gamete may undergo suppression at any 
period of the life-history, thus, in some instances of the rare production 
of male persons their occasional reappearance is undoubtedly due to 
the omission to suppress one or more of the forerunners of male-eggs. 
Similarly the rarity or the apparent absence, of a second form of 
spermatozoon in some instances is readily explicable. 
Of the problems of sex three aspects stand contrasted: these are 
its origin, its regulation, and its determination. Of its origin no 
absolutely certain knowledge is possible: probably it arose from an 
original isogamy passing into a heterogamy of fourfold gametes, thence 
passing ultimately to the present actual heterogamy of three forms 
of functional ones, with frequently a fourth but non-functional one. 
The experiments of Yuna, Born, PFLÜGER, Maupas, Mrs. TREAT 
and others are often regarded as dealing with the origin of sex during 
development, or with its determination. In fact these observers have 
endeavoured to regulate it; for they have all started from the erro- 
neous assumption, that the animals used in their experimental re- 
searches were either of no pre-destined sex or hermaphrodites. This 
error completely vitiates their results, which only prove what percen- 
tage of either sex will survive under given, usually utterly abnormal, 
conditions. 
