IX] OF LIESEGANG'S RINGS 431 



smaller intermediate rhythms, likewise manifested in certain cases 

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

 (for instance in Sesia spheciforniis), a pigmentation not concurrent 

 with the segmented structure of the antenna, is explicable in the 

 same way; and that the "ocelli," for instance 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 explanation! . To turn from the dis- 

 tribution of pigment to more deeply seated structural characters, 

 Leduc has shewn how, for instance, the laminar structure of the 

 cornea or the lens is again, apparently, 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 precisely the same appearance, save 

 that it is not quite so regular, is presented in one of K lister's 

 figures as the effect of precipitating a little sodium phosphate in 

 a gelatinous medium. Biedermann has studied, from the sanje 

 point of view, the structure and development of the molluscan 

 shell, the problem which Rainey had first attacked more than 

 fifty years before J ; and Liesegang himself has applied his results 

 to the formation of pearls, and to the development of bone§. 



* Descent of Man, ii, pp. 132-153, 1871. 



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 symmetrica] 

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

 disciission, 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 

 disturbance, somewhat as a series of concentric waves may be formed by the 

 splash of a stone thrown into a pool, etc." 



% Cf. also Sir D. Brewster, On optical properties of Mother of Pearl, Phil. Ti-ans. 

 1814, p. 397. 



§ Biedermann. W., Ueber die Bedeutung von KristaUisationsprozessen der 

 Skelette wirbelloser Thiere, namentlich der MoUuskenschalen, Z. /. allg. Physiol. 

 I, p. 154, 1902; Ueber Bau und Entstehung der MoUuskenschale, Jen. Zeitschr. 

 xxxvi, pp. 1-164, 1902. Cf. also Steinmann, Ueber Schale mid KalkstembUdungen, 

 Ber. Naturf. Ges. Freiburg i. Br iv, 1889; Liesegang, Naturw. Wochenschr. p. 641, 

 1910. 



