656 ON CONCRETIONS, SPICULES, ETC. [ch. 



closely resemble the little calcareous bodies in the tissues of a 

 trematode or a cestode worm, or in the oesophageal glands of an 

 earthworm*. 



When the albumin was somewhat scanty, or when it was mixed 

 with gelatine, and especially when a little phosphate of lime was 

 added to the mixture, the spheroidal globules tended to become 

 rough, by an outgrowth of spinous or digitiform projections; and 



Fig. 297. Large irregular calcareous concretions, or spicules, deposited in a piece 

 of dead cartilage, in presence of calcium phosphate. After Harting. 



in some cases, but not without the presence of the phosphatef, the 

 result was an irregularly shaped knobJ3y spicule, precisely similar 

 to those which are characteristic of the Alcyonaria%. 



The rough spicules of the Alcyonaria are extraordinarily variable in shape 

 and size, as, looking at them from the chemist's or the physicist's point of 

 view, we should expect them to be. Partly upon the form of these spicules, 

 and partly on the general form or mode of branching of the entire colony of 

 polyps, a vast number of separate "species" have been based by systematic 



* Cf. Claparede, Z.f.w.Z. xix, p. 604, 1869. On the structure of the moUuscan 

 shell, see O. B. Boggild, K. Vidensk. Selsk. Skr., Kjobenh., (9) ii, 1930. On nacre, 

 or mother-of-pearl, see Brewster, Treatise on Optics, 1853, p. 137; Schmidt, Die 

 Bausteine der Tierkorper in polarisirtem Licht, Bonn, 1924. Also S. Ruma Swamy, 

 Proc. Ind. Acad. Sci. (A), i, p. 871, 1935; P. S. Srinivasam, ibid, v, pp. 464-483, 

 1937; and, on the specific qualities of the nacre in the several divisions of the 

 Mollusca, Sir C. V. Raman, ibid. pp. 559, etc., 1935. 



t On the deposition of phosphates in organisms, cf. Pauli u. Samec, Biochem. 

 /Aschr. XVII, p. 235, 1909; Wiener mediz. Wochenschr. 1910, pp. 2287-2292. 



X Spicules much like those of the Alcyonaria occur also in a few sponges; cf. (e.g.), 

 V'aughan Jennings, Journ. Linn. Soc. xxiii, p. .")31, pi. 13, fig. 8, 1891. 



