268 BULLETIN OF THE 



among Arthropods. I am indebted to Dr. Hagen for references to the 

 following cases among insects : — 



1. Prionus coriarins with two perfect legs in place of the elytra.* 



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

 of the left antenna, f 



3. Zygoma filipendulae with one of the hind legs replaced by a 

 wing.J 



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 antennas 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, V 'ol. XXII. p. 191,1839; Stettin. Entomol. 

 Zeitung, Vol. I. p. 48 (cited from Hagen, 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. 



$ N. M. Kichardson, 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 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 antennae 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 antennse in Crustacea, A. Milne 

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

 V, 1 Abt., 1 Halfte, 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 

 parait avoir une autre valeur morphologique." (Bull. Acad. Boy. de Belgique, 2 Ser., 



