ORIGIN AND TRANSFORMATION OF ANIMALS. 
239 
have seen, be intercalated, and in this case our author calls 
the first ^coX^yi proto-scolex, thd second deuto-scolex, and so on, 
signifying first, second, &c., by Greek words. 
In the Medusa we saw that each egg which it laid pro¬ 
duced not a single Medusa, as a butterfly’s egg yields a single 
butterfly, but a great number of individuals. Secondly, this 
reproduction took place in an indirect or mediate way; for 
between two generations of Medusa several generations of 
very different creatures were produced by budding. To speak 
in a still more general way, it is a case of multiple generation 
by the aid of a single germ* It is that which I have endea¬ 
voured to express by the word geneagenesis, which is applicable 
to every method of reproduction that exhibits this charac¬ 
teristic feature.” The common polyp multiplies by buds, 
and also by eggs; but when it lays eggs it dies. Thus from 
the polyp egg comes a single individual, a scolex, capable of 
producing others like itself, which can bud in their turn, and 
repeat the process, and which end, like the original stem 
animal, in acquiring sexual attributes. ‘^It is as if there 
came from the egg of a butterfly an animal having the ap¬ 
pearance of a perfect insect, but destitute of reproductive 
organs, although able to give rise by budding to individuals 
like itself, and which, together with itself, would ultimately 
acquire the attributes of a father and mother.” In such in¬ 
stances geneagenesis is reduced to its simplest elements, 
each scolex transforms itself into a proglottis, and the stro- 
bila stage does not appear. 
Among the Ascidians, of which the Salpa may be taken as 
an example, “ the scolex transforms itself directly into a pro¬ 
glottis, which in its turn produces a whole generation of in¬ 
dividuals like itself. . . . , In this case, to follow out 
comparison, it is as if the butterfly’s egg produced a cater¬ 
pillar, which arrived at a perfect state, and afterwards, from 
the butterfly coming from the primitive egg, other butterflies 
had sprung, of which it was neither the father nor the mother, 
but only the parent.” With the plant-lice we arrive at fur¬ 
ther complications. ‘^The egg laid in autumn engenders a 
scolex, having the,character of a nymph or pupa. During 
the spring this nymph does not lay eggs, but forms buds, 
which arise and organize themselves in the interior of its body, 
instead of making their appearance and developing them¬ 
selves on the outside, as with the polyps and the Medusae. 
When the temperature falls, the normal reproductive appa¬ 
ratus shows itself in distinct individuals, and then we find 
males and females, that is to say, true proglottis,^’ M. Qua- 
trefages does not consider that the main facts demand any 
