196 Mr. J. O. Westwood's Description 



in the other specimen. The thorax on the upper side is marked 

 with a large oblong dark mark, but which is neither so dark 

 coloured nor so large as in Ocellatus. In Populi there is no trace 

 of this mark. 



Hence we see, that with the exception of the markings of the 

 anterior wings, there is a far greater tendency to Ocellatus (the 

 male parent) than to Populi in tliese hybrids. 



In the higher animals the occurrence of hybrids is so frequent 

 as to leave no doubt as to the power of generation between 

 two distinct but allied species of animals : the only question 

 being, whether these hybrids are or are not fertile ? a question 

 to be solved only by experiment, and a very careful compara- 

 tive investigation of the structure of the organs of generation. 

 It is the general opinion that hybrids are not productive, but if, 

 as in the case of the moths under observation, the individuals 

 exhibit all the external characters of one or the other sex, the 

 non-possession of the power of generation must originate in some 

 organic internal deficiency which requires investigation. Instances, 

 it is true, are upon record, of fertile hybrids between the common 

 gander and the Chinese goose (which hybrids had bred between 

 themselves), between the Chinese boar and the common pig, and 

 between two species of geese {Anas hoschus and A. acuta). These 

 instances were mentioned by various naturalists at the Bristol 

 Meeting of the British Association, August, 1836; but they 

 appear to have been considered to have originated in some mis- 

 take or oversight. (See Athenaeum, 1836, p. 634.) 



Mr. Eyton, however, in a more recent communication, published 

 in the Magazine of Natural History for July, 1837, has clearly 

 substantiated some of these, but leaving it in doubt whether or 

 not this fact did not prove that the supposed parent-species ought 

 only to be regarded as varieties rather than species, but leaning 

 to the contrary opinion. 



Mr. Eyton has since informed me that he has succeeded in 

 breeding from the hybrids between the common and Chinese geese 

 for three generations. 



The same gentleman, on the 12th May, 1835, read some account 

 before the Zoological Society of a hybrid bird, between the cock 

 pheasant, Phasianus Colchicus, Linn., and the grey hen, Telrao 

 perdix, Linn., and of which he had made an anatomical investiga- 

 tion. In this instance the specimen, although a female, is ex- 

 pressly stated to have the left oviduct very imperfect, the ovaries 

 very small, the eggs scarcely perceptible and very few in number ; 

 the plumage of the bird was also very curious, some parts of it 



