262 
GEOFFREY SMITH. 
blood by an excess of fatty substance, only occurs to a con- 
siderable extent in the case of Inachus, and accordingly we 
find that this crab is influenced in every respect far more 
profoundly by the presence of the parasite than is the case in 
C a r c i n u s . 
To this point in the analysis of the effect on Sacculiua 
on its host we have at present arrived, and though it is 
impossible to claim that the explanation is complete, yet we 
would crave the reader's indulgence while we remind him of 
the steps that have been won in advance of the position 
gained by Griard when he discovered the phenomenon of 
“parasitic castration." At that time the interpretation 
universally put upon the phenomenon was that the parasite 
caused the atrophy of the internal reproductive organs, and 
in consequence the secondary sexual characters of both sexes 
underwent correlative alterations, the male being assimilated 
to the female, and the female to the male. 
The first step in advance of this interpretation was gained 
by showing that the alteration was always in the female 
direction, the female individuals never assuming any male 
characters under the influence of the parasite, whereas the 
male is frequently so highly modified towards the adult 
female state, both externally and internally, as to be easily 
mistaken for a true female. The next step was to show that 
not only was the male altered into the female condition, but 
also the young females themselves were forced under the 
influence of the parasite to assume prematurely the adult 
female characters. 
The whole reaction, therefore, so far from being a 
passive result of the destruction of the gonad, was found 
to be an active assumption in both sexes of adult female 
characters, despite the entire absence of a functional ovary. 
A further step was gained by seeking in the internal con- 
dition of the animal's metabolism for the cause of these 
changes. It was clear that the old and familiar idea of an 
internal secretion produced by the gonad being the 
stimulus for the development of the secondary sexual 
