Theorie des formations et des
deformations organiques appliquee a l'anatomie comparee des
monstruosites_ (1832), and in his final large memoir of 1860 (see below,
p. 205).

In 1816 appeared a fine piece of work by J. C. Savigny on the homologies
of the appendages in Articulates. The standpoint was that of pure
morphology. "I am convinced," he wrote, "that when a more complete
examination has been made of the mouth of insects, properly so called,
that is to say, having six legs and two antennae, it will be found that
whatever form it affects it is always essentially composed of the same
elements.... The organ remains the same, only the function is modified
or changed--such is Nature's constant plan."[135] In this the influence of
Geoffroy can be traced; but the work was very free from the
exaggerations of the transcendentalists, and many of Savigny's
homologies are accepted even to-day. The first memoir dealt with the
mouth-parts of insects; the second with the anterior appendages of
Articulates generally. Savigny shows that the mouth-parts of insects can
be reduced to the type shown in Orthoptera, where there are clearly two
mandibles, two maxillae, and a lower lip formed by the fusion of two
second maxillae. All other insects have these same mouth-parts, disposed
in the same order, however much their form may have been modified in
response to new functions. He goes on to compare the anterior set of
appendages in a long series of Articulates, in _Julus_, _Scolopendra_,
_Cancer_, _Gammarus_, _Cyamus_, _Nymphon_, _Phalangium_, _Apus_,
_Caligus_, _Limulus_, and a few others. For Crustacea he established the
homologies now accepted, of the mandibles with the mandibles of insects,
of the first and second pairs of maxillae with the parts so named in
insects, and so on. He is quite clear that the maxillipedes of Crustacea
are the homologues of the feet of Hexapoda. "Their disposition must lead
one to think that the six anterior feet of _Julus_, that is to say, all
the feet of the Hexapoda, are here transformed into jaws" (_loc. cit._,
p. 48). In _Scolopendra_ also there is a similar transformation of two
pairs of legs into auxiliary jaws. In _Gammarus_, where there is only
the first pair of maxillipedes, the other two pairs have become
"retransformed" into feet. We find him supporting his comparison of the
three anterior pairs of legs in _Julus_ to the three pairs of legs in
insects by an argument drawn from embryology; for on