is deposited from a well-defined portion of the protoplasm (chitosarc, 

 Wallich), and not upon the outside of the body, but between two 

 chitinous lamellae situated in the 

 ectoplasm (Fig. 149). The manufac- 

 ture of the shell material of the 

 Mollusca was explained by Stein- 

 mann as a purely chemical phenome- 

 non, and not as an expression of vital 

 activity. The early experiments of 

 Harting ('73) in allowing carbonic 

 acid alkalies to act upon albumin or 

 other nitrogenous substances, there- 

 by obtaining a precipitate of calcium 

 carbonate in the form of granules 

 similar to Coccoliths, gave Steinmann 

 the clue to his theory that calcium 

 chloride and other salts acting upon 

 albumin in animal protoplasm give a 

 similar precipitate. Applying this 

 theory to the marine rhizopods, 

 Dreyer argued that the protoplasmic 

 body is saturated with dissolved cal- 

 cium salts, and that albuminoid stuffs 

 secreted by the living animal undergo 

 fermentation through the agency of 

 bacteria, and ammonium carbonate is 

 formed, which, acting upon the cal- 

 cium salts, results in the formation 

 of calcium carbonate. 1 A similar 

 explanation can be given for the 



diverse skeletons of the Radiolaria, the precipitate here collecting in. 

 the interstices of the protoplasmic alveoli, thus giving rise, first to 

 the four-rayed type of spicule, and then to the compact skeletons 

 (Fig. 41, p. 77). 



Among the most interesting materials secreted by the Protozoa 

 are those which give rise, through rapid oxidation, to phosphorescence. 

 A great many forms have this power, especially among the Dino- 

 flagellidia and the Cystoflagellidia; and although the cause is not fully 

 established, yet it is generally agreed, at the present time, that the 

 light is due to the rapid oxidation of certain products of metabolism. 

 One of the most noteworthy illustrations of phosphorescence is shown 

 by Noctilnca miliaris, in which Quatrefages ('50) found that the light, 



Fig. 149. Shell formation in Gromia 



jluviahlis Duj. [DREYER.] 

 /, the deposit between two lamella. 



1 Cf. Dreyer, p. 224. 



