THE PAST AND PRESENT OF THE CUTTLEFISHES. 



history and progress of the theory of evolutiop/^rrridst ''the j 

 warfare through which in the days of its youth' it was fated 'to pass/ 

 will remember the somewhat famous controversy regarding the eyes 

 of cuttlefishes and their relations with vertebrate eyes, in which Mr. 

 Darwin and Mr. St. George Mivart took part. The latter, insisting 

 upon the likeness of the cuttlefish eye to the vertebrate eye, laid stress 

 upon this likeness to enforce his argument that, as such likeness 

 could not be "due to inheritance from a common progenitor, it would 

 be difficult if not impossible to explain such likeness as arising by 

 the slow variation postulated by Darwin's theory of natural selection." 

 Mr. Mivart's words are clear enough. Speaking of the presumed 



ONI 



FIG. 7. DEVELOPMENT OF THE CUTTLEFISH EYE. 



A, Section of eye of Nautilus ; B, of Two-gilled Cuttlefish ; c, of a Snail ; D and E, Early stages 

 in formation of eye. References correspond in all the figures : L 1 L 2 , lens ; I R, iris ; S s, 



cornea ; R, retina ; o N, optic nerve. 



likeness between the eyes of vertebrates and cuttlefishes, he says, 

 " There can hardly be any hesitation in saying that for such an exact, 

 prolonged, and correlated series of similar structures (sclerotic, retina, 

 choroid, lens, &c., of the eye) to have been brought about in two 

 independent instances by merely indefinite and minute accidental 

 variations, is an improbability which amounts virtually to impossi- 

 bility." 



The primary difficulty, that of the development of the eye 

 in any group by gradual and progressive modification, is, however, 

 solved and obliterated by the history of the individual development 

 of any single eye in that group. Mr. Mivart's specific difficulty, that 

 of the causes of the likeness between cuttlefish eyes and vertebrate 

 eyes, vanishes away when the progress of research demonstrates that 

 the likeness in question is only apparent. For in truth there exists 



