254 



NICOLAUS STENO 



P. 68. 5. Was able to open itself at times in proportion to the 



size of the angle which the hinges of the shells allow. 



6. Grew from a small to a large size. 



7. Transmitted through its own substance the matter of 



which the subdivisions of shell were made. 



As regards the outer matter surrounding mussels: (i) If 

 it was not wholly a fluid, at least its power of resistance was 

 less than the power of expansion inherent in the substance 

 within the shells. (2) It contained a fluid substance suited 

 to the formation of the filaments of the subdivisions of 

 shell. 



All these conditions of both the inner and the outer place, 

 which are proved by arguments and drawings in the Disserta- 

 tion itself, fully show that there was an animal within the shells, 

 and a fluid without the shells. 



The second class consists of those shells which are in other 

 respects like those just described, but differ from them in color 

 and weight. While some are lighter, others are heavier, 

 because the heavier shells have their pores filled with an 

 extraneous fluid, while the pores of the former have been 

 enlarged by the ejection of the lighter parts ; I add nothing fur- 

 ther in regard to them because they are nothing but the shells 

 of animals, either petrified or calcined. 



The third class consists of shells which in form only are 

 similar to those just described, in other respects differing from 

 them completely; since neither subdivisions nor filaments, 

 much less differences of filaments, are found in them. Some 

 of these are filled with air; others, either black or yellow in 

 P. 59. color, with stone ; others with marble ; others with crystal ; and 

 still others with other matter. The formation of all of these 

 I account for in the following way. 



When the penetrating force of fluids has dissolved the sub- 

 stance of a shell, the fluids have either been drained away by 

 the earth, leaving empty spaces in the shells (which I call shells 

 filled with air),^ or have been changed by the addition of new 

 matter and have filled the spaces in the shells with crystals or 

 marble or stone, according to the diversity of the matter. And 



1 The Latin phrase is iestas aereas ; porous shells are meant. 



