56 Evolution and Adaptation 
the point; but the issue thus raised is too unimportant to 
merit further discussion. Leaving aside also some even more 
doubtful criticisms which are made by Fleischmann, and 
which might be added to indefinitely without doing more 
than showing the credulity of some of the more ardent 
followers of the transmutation theory, or else the uncertainty 
of some of the special applications of the theory, let us pass 
to Fleischmann’s criticism of the problem of development.! 
With fine scorn Fleischmann points to the crudity of the 
ideas of Oken and of Haeckel in regard to the embryology 
(or the ontogeny) repeating the ancestral history (or the 
phylogeny). We may consider briefly (since we devote the 
next chapter almost entirely to the same topic) the excep- 
tions to this supposed recapitulation, which Fleischmann has 
brought together. The young of beetles, flies, and butter- 
flies creep out of the egg as small wormlike forms of appar- 
ently simple organization. They have a long body, composed 
of aseries of rings; the head is small and lacks the feelers, 
and often the faceted eyes. The wings are absent, and the 
legs are short. At first sight the larva appears to resemble a 
worm, and this led Oken to conclude that the insects appear 
first in the form of their ancestors, the segmented worms. If 
we examine the structure of the larva more carefully, we shall 
find that there are a great many differences between it and 
the segmented worms; and that even the youngest larva is 
indeed a typical insect. The tracheze, so characteristic of the 
group of insects, are present, the structure of the digestive 
tract with its Malpighian tubes, the form of the heart, the 
structure of the head, as well as the blastema of the repro- 
ductive organs, show in the youngest larva the type of the 
insects. In other words the body of the caterpillar is formed 
on exactly the same fundamental plan as that of the butterfly. 
1 The long argument of Fleischmann in regard to the origin of the fresh- 
water snails, as illustrated by the planorbis series, and also the origin of the 
nautiloid group, has been recently dealt with fully by Plate, and, therefore, need 
not be considered here. 
