242 



LIFE, IN ITS INTERMEDIATE FORMS. 



Like all organic functions, the action of these cilia is 

 not under the will of the animal. If. during life, a small 

 portion of the gills be cut off, the motion of the cilia will 

 convey the fragment swiftly away, with a smooth easy mo- 

 tion, through the surrounding fluid, in a definite direction. 

 It does not even cease with the life of the animal. A 

 specimen which we examined had been dead at least 

 fifteen hours, yet when we placed the torn fragments of 

 the branchial, one after another, beneath the microscope, 

 the energy of the ciliary action, as the wave flowed with 

 uniform regularity up one side and down the other of 

 every filament, filled us with astonishment. Even the 

 next morning, twenty-six hours after death, when the 

 tissues of the filaments were partially dissolved, the ciliary 

 motion was still going on, on portions that preserved their 

 integrity. XO\w)^(7yv<M-' 



The leaved which form the mantle are useful, not only 

 for protecting these gills and the other delicate organs 

 which are situated within their embrace, but for manu- 

 facturing the valves of the shell. This process has been 

 ably described by Professor Rymer Jones, as it takes place 

 in the Scallop (Pecten maxi?nus), and we shall quote his 

 words : — 



" It is the circumference or thickened margin of the 

 mantle alone which provides for the increase of the shell 

 in superficial extent. On examining this part, it is found 

 to be of a glandular character, and, moreover, not 

 unfrequently provided with a delicate and highly sen- 

 sitive fringe of minute tentacula. Considered more 

 attentively, it is seen to contain in its substance patches 

 of different colours, corresponding both in tint and rela- 



