IX] OF SCALES AND OTOLITHS 665 



point of view, the structure and development of the molluscan shell, 

 the problem which Rainey had first attacked more than fifty years 

 before*; and Liesegang himself has applied his results to the 

 formation of pearls, and, as Bechhold has also done, to the develop- 

 ment of bonef. 



The presence of concentric rings or zones in slow-growing 

 structures is evidently after some fashion a function of the time, 

 and an indication of periodic acceleration or variation of growth; 

 it is apt to be referred, rightly or wrongly, to the seasons of the 

 year, and to be interpreted (with or without confirmation and proof) 

 as a sure mark and measure of the creature's age. This is the case, 

 for instance, with the scales, bones and otoliths of fishes; and a 

 kindred phenomenon in starch-grains has given rise, in like manner, 

 to the belief that they indicate a diurnal and nocturnal periodicity 

 of activity and rest J on the part of the cell wherein they grew. 



That this is actually the case in growing starch-grains is often 

 if not generally beheved, on the authority of Meyer §; but while 

 under certain circumstances a marked alternation of growing and 

 resting periods may occur, and may leave its impress on the structure 

 of the grain, there is now more reason to beheve that, apart from 

 such external influences, the internal phenomena of diffusion may, 

 just as in the typical Liesegang experiment, produce the well-known 

 concentric rings. The spherocrystals of inulin, in like manner, 

 shew, like the calcospherites of Harting (Fig. 307), a concentric 

 structure which in all likelihood has had no causative impulse save 

 from within. 



The striation, or concentric lamella tion, of the scales and otoHths 

 of fishes has been much employed, not as a mere indication, but 



* Cf. also Sir D. Brewster, On optical properties of mother of pearl, Phil. Trans. 

 1814, p. 397; and J. F. W. Hersehel, in Edin. Phil. Journ. ii, p. 116, 1819. 



f VV. Biedermann, Ueber die Bedeutung von KristaUisationsprozessen der 

 Skelette wirbelloser Thiere, naraentlich der Molluskenschalen, Z. f. allg. Physiol. 

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

 XXXVI, pp. 1-164, 1902. Cf. also Steinmann, Ueber Schale und Kalksteinbildungen, 

 Ber. Naturf. Ges. Freiburg i. Br. iv, 1889; Liesegang, Naturw. Wochenschr. 1910. 

 p. 641; Arch. f. Entw. Mech. xxxiv, p. 452, 1912; H. Bechhold, Ztschr. f. phys. 

 Chem. Lii, p. 185, 1905. 



X Cf. Biitschli, Ueber die Herstellung kiinstlicher Starkekorner oder von 

 Spharokrystallen der Starke, Verh. nat. med. Ver. Heidelberg, v, pp. 457-472, 1896. 



§ U ntersuchiLngen ilber die Stdrkekorner, Jena, 1905. 



