264 BULLETIN OF THE 
claw. The amputated part was evidently removed when the shell was 
soft, and the wound has completely healed. The dactylus has the form 
of a cylindrical stunted segment, with an imperfectly developed line of 
teeth on its cutting surface. The character of the shell leads me to 
believe that the amputation passed through the line indicated by x, and 
that the part of the hand distal to this, as well as the dactylus, was re- 
produced by budding after the wound was received. | 
Although as early as 1671 the fanciful Von Berniz (No. 1) described 
and figured two misshapen Crustacean claws, the number of deformities 
among animals of this class recorded by naturalists is small compared! 
with those observed in insects. Of the thirty cases which I find hith- 
erto recorded, fifteen belong to the European crayfish (Astacus fluviati- 
lis).* Leaving out of account the claw represented by Fig. 3 on Plate 
IL, in which we have a simple distortion arising from an abnormal 
curvature of the fingers, it appears that all the deformities just de- 
scribed belong to the two categories of monstrositates per defectum and 
monstrositates per accessum. The former (such as Plate II. figs. 7, 9) 
are without doubt the result of an accidental amputation of certain 
parts when the animal was soft-shelled, which parts would probably 
have been restored after subsequent moults if the animal had lived. 
Such deformities can hardly be termed true monstrosities, and are of 
minor interest. The latter, —in which category all the other cases 
figured will be included, — while accompanied in most cases by a dis- 
tortion of normal structures, and probably for the most part the result 
of injuries, present irregular, secondary outgrowths, and are of consider- 
able interest. Among these we have, first, cases of duplication of joints 
in a limb (as in Plate I. figs. 12, 13, 16, Plate IT. fig. 6), similar to the 
many cases described among insects ; secondly, processes budding out from 
either the propodus (Plate I. figs. 9, 11, 14, 17) or the dactylus (Plate I. 
figs. 1-8, 15, Plate II. figs. 1, 4, 5) without any articulation. These 
processes frequently simulate a true claw in a marvellous manner, e. g. 
Plate I. figs. 1-5, and are worthy of especial attention. A Crustacean claw 
is, morphologically viewed, a composite structure involving two segments 
of the series of seven which are found in the typical leg. The ultimate seg- 
ment of the series develops teeth along its inner border, and when flexed 
closes against an immovable toothed process from the penultimate seg- 
ment. But in these fictitious claws (sce Plate I. figs. 2, 5, etc.) the two 
* [t is remarkable that in the vast number of American crayfishes examined by 
Hagen in the preparation of his Monograph of the North American Astacidæ, no 
deformities, strictly speaking (see p. 269), were observed. 
