120 



PROFESSOR HARTING. 



fact of their mutual adhesion, when they are developed in the 

 neighbourhood of one another. The most simple case is that 



Fig. 2. 



of those double bodies {dumb-bells, Fig. 1) which are often 

 prodviced in very large quantities, and which, as well as the 

 lenticular calcospherites, recall the coccohthes and cyatholithes 

 of Bathybius. Agglomerations of calcospherites, in more or 

 less considerable groups (Fig. 3, a), or sometimes in plates 



Fig. 3. 



(Fig. 3, b), may, moreover, be formed in different manners, 

 and in this way polyhedric bodies are developed, which, so 

 far as their shape is concerned, have a great resemblance to 

 cells. Thus may be explained, also, the structure of the ex- 

 ternal layer of the shells of various Lamelhbranchiata, and of 

 some Gasteropoda, which are ajDparently composed of cells 

 arranged in columns. 



In certain definite circumstances the calcium carbonate, 

 combined with albumen, forms very thin curved laminae, 

 which have nothing in common with calcospherites, and pre- 

 cisely resemble the calcareous plates of the bone of the sepia. 

 At the same time they enable us to understand the mode of 

 development of other amorphous calcareous plates, and espe- 

 cially those of the shells of Foraminifera and the loculi of the 

 Bryozoa. 



