14 
to shelter himself under the example of nature. One thing we can 
do, we can appeal to her to warn him of the dire consequences of 
parasitism, of which crime she is a stern and invariable Punisher. 
She deprives the bats and insects of eyes if they shun the light of 
day, and retreat into the darkness of caves; and similarly she has 
deprived the Hermit Crab of his shell and one of his claws and 
the Sacculina of well-nigh everything it once possessed. The 
diagram shows you ils capabilities in its youth ; it comes from the 
egg endowed with three pairs of swimming organs; as it moults 
it becomes enclosed in a thin bivalve test or shell; then by means 
of the hooks which have now appeared on its front limbs it fixes 
itself on some unfortunate hermit who happens to be changing his 
habitation ; ‘the sight of means to do illdeeds makes (another) ill 
deed done,”’ after which the Sacculina subsides into quiescence. 
“‘Corpulent, blind, legless cripples, their existence is more pre- 
carious than that of the most miserable, mutilated beings found in 
our cities, they only live on the blood of the neighbour which gives 
them an asylum. Yet when they first quit the egg they are all 
free ; they trisk, they swim with the rapidity of lightning, and at 
the close of life we find them deformed, and crouched in some 
living refuge, as if a foul leprosy had atrophied within them all the 
organs which served as a means of communication with the outer 
world.” (Van Beneden). 
In the previous instances we note that the degeneration attaches 
to the latter stages only of the animal’s existence. We might 
almost imagine, I do not know why we should not, that there is 
still for each of them a possibility of regaining the lost ground, 
still a chance for an upward movement in the battle of life, seeing 
that the early stage is already a high one. There are other 
Parasites, however, the degradation of which is far more thorough 
and complete, since it is patent throughout the creature’s whole exist- 
ence. It is born a parasite, and it remains one till death. Like a 
nation utterly irreclaimable and depraved, in which there is no 
tendency or opportunity, not even the desire, in any one individual, 
to reach up after better things. It is a degeneration of the whole 
kind, species, or it may be genus. Hatched from the egg in the 
body of a higher animal, it takes up its abode there permanently, 
or it passes by a strange transmigration into the body of another, 
higher still, maybe even into our own, and perfects itself there. 
Iam thinking especially of the internal parasites, the HEntozoa, 
whose life histories are as marvellous as any of those I have related. 
The suitability of their organization for their functions is as com- 
plete as our own Without organs of sense or digestion, none of 
which are needed, they are well supplied with those of prehension, 
‘in the form of suckers and hooks, by means of which they attach 
