268 BULLETIN OF THE 
among Arthropods, I am indebted to Dr. Hagen for references to the 
following cases among insects : — 
1. Prionus coriarius with two perfect legs in place of the elytra.* 
9. Cimbex axillaris with a claw like those of the tarsi, on the end 
of the left antenna.T 
3. Zygena filipendulo with one of the hind legs replaced by a 
wing. $ 
Among Crustacea the only example of this kind of monstrosity is the 
Palinurus penicillatus described by A. Milne Edwards (No. 12), in which 
a flagellum like one of those of the antennules is developed from the 
centre of a rudimentary cornea on the end of the eye-stalk. 
Monstrosities of this class are especially interesting on account of their 
bearing on the morphology of organs. If we admit teratological con- 
ditions as evidence of homology, as the botanists do in the case of the 
metamorphosis of the parts of a flower, we must regard the wings and 
legs of insects, as well as the eye-stalks and antennæ of. Crustacea, as 
morphological equivalents,$ a view which is not supported by the mode 
of development of these parts in the embryo. 
* Saage, Preussische Provinzial Blatter, Vol. XXII. p. 191, 1839; Stettin. Entomol, 
Zeitung, Vol. I. p. 48 (cited from Hagen, On some Insect Deformities, Mem. Mus. 
Comp. Zoël., Vol. II. No. 9, p. 22, 1876). 
1 G. Kraatz, Ueber eine merkwiirdige Monstrosität bei Cimbex axillaris (Hymen- 
opt.), Deutsche Ent. Zeits., XX. Heft IT. p. 377, Taf. L fig. 8 a, a, b, 1876. 
1 N. M. Richardson, Nature, Vol. XVI. p. 361, August 30, 1877. Dr. Hagen 
tells me that he is sure he has seen another similar case recorded, but he has lost the 
reference to it. 
$ Dr. Hagen (in his lectures) also adduces evidence from comparative anatomy of 
insects to support the theory of the homology of wings and legs. Most authors 
(Gegenbaur, Lubbock, Fritz Müller, etc.) who have discussed the question of the 
morphology of insects' wings consider them to have originated independently of the 
ventral appendages, as tracheal gills or otherwise. Balfour (Treatise on Comparative 
Embryology, Vol. I. p. 337, 1880) even doubts whether the antennæ of insects have 
the same morphological value as the succeeding appendages! None of these writers 
take notice of the above-mentioned monstrosities in this connection. 
With reference to the homology of eye-stalks and antenne in Crustacea, A. Milne 
Edwards (No. 12), Gerstaecker (Bronn's Klassen und Ordnungen des Thier-Reichs, 
V., 1 Abt., 1 Hälfte, pp. 202, 343, 1868), and Rolleston (Forms of Animal Life, pp. 
113, 119, 1870) bring forward the abnormal development of an antennulary flagellum 
from the eye-stalk in the Palinurus mentioned above as proof of the homology of the 
eye-stalk with the antenna, a view long ago advanced by Savigny and H. Milne Ed- 
wards. The embryologists on the other hand, as Claus and Fritz Miiller, generally 
deny the equivalence of the parts in question. E. van Beneden says of the eye- 
stalk in Mysis : “ Ce pedicule n'apparait aucunement comme les autres appendices, et 
varaît avoir une autre valeur morphologique.” (Bull. Acad. Roy. de Belgique, 2 Ser., 
