J- <*.^,w 



PROFESSOR HARTING. 



shell of the Gasteropoda. On other plates may be observed 

 thickened patches, arranged in parallel bands, similar in 



Fig. 4. 



appearance to those which exist on the external layer of 

 the scales of osseous fishes (Fio^. 5, a). 



In order to obtain these different forms of plates it is 

 necessary to make use of albumen. Under the influence of a 

 low and constant temperature there are developed, both on the 

 calcospherites and on the plates, curved spinous projections 

 (Fig. 5, b). Ifthe liquid contains, in addition, gelatine, other 

 projections are developed upon many of the calcospherites ; 

 but they then have a warty appearance, and themselves have 

 upon them secondary smaller projections, or else they branch, 

 till at length they come to resemble, precisely, the spicules 

 or sclerites of Alcyonaria (fig. 6, a). Sclerites of the same 



Fig. 



Fig. e. 



kind, although slightly diff'erent in form (Fig. 6, b), are also 

 developed in cartilage, which is first impregnated with a 

 solution of calcium chloride, and then placed in a solution 

 of potassium carbonate, mixed with a little sodium phosphate. 



