LIFE OF THE WIDER SEAS 105 



gent paths of variation. The lesson we may read in these 

 facts seems plain ; it is to the effect that environment alone is 

 not always competent to determine the way followed by a 

 species in its process of change. 



In the sunlit regions of the surface of the open oceans, 

 even in the under water of the sea, down to the utmost 

 depths to whicli the light penetrates, we have a zone of 

 waters in which the variety of form is limited, and the greater 

 part of them belong to the lower orders of being. From this 

 part of the sea few fishes have been obtained, for the creatures 

 are able to dwell only where there is an abundance of food. 

 In this zone the most interesting forms are the lowly protozoa 

 wdiose bodies, to the eye, appear as mere bits of translucent 

 jelly, essentially unorganized, but which secrete shapely shells, 

 showing that the apparent simplicity which they present to 

 our eyes is due to our imperfect knowledge of them. Dwell- 

 ing in myriads in the superficial parts of the sea, these foram- 

 inifera, as they are termed, sink at death to the bottom, over 

 which they accumulate a thick coating of minutely divided 

 limestone powder, forming a layer of ooze as unsubstantial 

 as the finest snow. A large part of the North Atlantic, par- 

 ticularly that vast level tract beneath the central portion of 

 the sea, known as the telegraphic plateau, because it was 

 crossed by the first telegraphic cable which was laid, is cov- 

 ered with this chalk-like substance. Along with these shelly 

 bits derived from animals which have dwelt near the surface, 

 there go into the waste which accumulates on the floor, the 

 remains of creatures which dwelt upon the bottom ; thus it 

 comes about that the fossils which we find in any stratum may 

 have been nurtured under very various conditions: in part 

 they may have dwelt on the floor of the deep sea, in the cold 



