664 ON CONCKETIONS, SPICULES, ETC. [en. 



phenomenon a very long way, in the explanation of various banded, 

 striped, and other rhythmically successional types of structure or 

 pigmentation. The striped leaves of many plants (such as Eulalia 

 jajponica), the striped or clouded colouring of many feathers or of 

 a cat's skin, the patterns of many fishes, such for instance as the 

 brightly coloured tropical Chaetodonts and the like, are all regarded 

 by him as so many instances of "diffusion-figures" closely related 

 to the typical Liesegang phenomenon. Gebhardt* declares that the 

 banded wings of Papilio podalirius are analogous to or even closely 

 imitated in Liesegang's experiments; that the finer markings on 

 the wings of the goatmoth shew a double rhythm, alternately 

 coarse and fine, such as 'is manifested in certain experimental cases 

 of the same kind ; that the alternate banding of the antennae (for 

 instance in Sesia spheciformis), a pigmentation not concurrent with 

 the antennal joints, is exphcable in the same way; and that the 

 ocelli on the wings of the Emperor moth are typical illustrations 

 of the common concentric type. Darwin's well-known disquisition 

 on the ocellar pattern of the feathers of the Argus pheasant, as a 

 result of sexual selection, will occur to the reader's mind, in striking 

 contrast to this or to any other direct physical explanationf. 



To turn from the distribution of pigment to more deeply seated 

 structural characters, Leduc has argued, for instance, that the 

 laminar structure of the cornea or the lens is, or may be, a similar 

 phenomenon. In the lens of the fish's eye, we have a very curious 

 appearance, the consecutive lamellae being roughened or notched 

 by close-set, interlocking sinuosities; and the same appearance, 

 save that it is not quite so regular, is presented in one of Klister's 

 figures as the effect of precipitating a little sodium phosphate in 

 a gelatinous medium. Biedermann has studied, from the same 



* Verh. d. d. zool. Gesellsch. p. 179, 1912. 



t As a matter of fact, the phenomena associated with the development of an 

 "ocellus" are or may be of great complexity, inasmuch as they involve not only 

 a graded distribution of pigment, but also, in "optical" coloration, a symmetrical 

 distribution of structure or form. The subject therefore deserves very careful 

 discussion, such as Bateson gives to it ( Variation, chap. xii). This, by the way, 

 is one of the very rare cases in which Bateson appears inclined to suggest a purely 

 physical explanation of an organic phenomenon: "The suggestion is strong that 

 the whole series of rings (in Morpho) may have been formed by some one central 

 disturban(»e, somewhat as a series of concentric waves may be formed by the splash 

 of a stone thrown into a pool." Cf. Darwin, Descent of Man, ii, p. 132, 1871. 



