208 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.* 



2. Cimbex axillaris with a claw like those of the tarsi, ou the end 

 of the left antenna, f 



3. Zt/gccna Jilipendulce with one of the hind legs replaced by a 

 wing.:}: 



Among Crustacea the only example of this kind of monstrosity is the 

 Palinur us penicillatus described by A. Milne Edwards (No. 12), in which 

 a flagcllum 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 antennee of Crustacea, as 

 morphological equivalents, § a view which is not supported by the mode 

 of development of these parts in the embryo. 



* Saage, Prcicssische Provinzial BlciUer,\o]. XXII. p. 191,1839; SfcUi7i. Entomol. 

 Zeitung, VoL I. p. 48 (cited from ^lagen, On some Insect Deformities, Mem. Mus. 

 Comp. ZooL, VoL II. No. 9, p. 22, 1876). 



t G. Kraatz, Ueber eine merkwiirdige Monstrositat bei Cimbex axillaris (Hymen- 

 opt.), Deutsche Ent. Zeits., XX. Heft II. p. 377, Taf. I. fig. 8 a, a, b, 1876. 



t 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 ho 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 

 (Gcgenbaur, Lubbock, Fritz Miiller, 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 antenn.ne of, insects liave 

 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 antennae in Crustacea, A. Milne 

 Edwards (No. 12), Gerstaecker (Bronn's Klasscn und Ordnungen des Thier-Reichs, 

 v., 1 Abt., 1 Hiilfte, pp. 202, 343, 18C8), and Rolleston (Forms of Animal Life, i>i). 

 113, 119, 1870) bring forward the abnormal development of an antennulary flagelhiin 

 from the eye-stalk in the Palimcrus mentioned above as proof of the liomology of the 

 eye-stalk with the antenna, a view long ago advanced by Saviguy and 11. Jlilne 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 Mysia : " Ce pedicule n'apparait aucuncment comme les autrcs appendices, et 

 Jjaralt avoir une autre valcur mori)hologique." {Bull. Acad. Roy. de Belgique, 2 Ser., 



