the Animals of the Deep Seas. 199 



lata, Hydrohia ulvce^ Jcera alhifrons^ and Polynoe cirrosa crept 

 about upon it upwards and downwards or buried themselves 

 in the soft mass. 



Third day. A mixture of sand and finely comminuted shells 

 from the harbour was laid upon the highest part of the slope. 

 This addition formed a wedge of 6 centims. length, with an 

 inclination of 25-26°. 



On the fourth, fifih, and sixth days the water was set in 

 motion for a few minutes, at the surface, by means of a glass 

 rod. 



On the seventh day the greater part of the comminuted 

 shells and sand had sunk in. 



On the ninth day scarcely anything but organic mass was 

 to be seen at the surface. The angle of inclination of the 

 slope had sunk from 26° to 20°. The reentering curve at its 

 lower end was almost entirely filled up, and the horizontal 

 part of the bottom covered with mud-particles to a thickness 

 of from 1 to 2 millims. 



Tenth day. The temperature of the water was 12'5° R. 

 ( = 60° F.). Over the highest part of the heap of soil (close 

 to the shore) a wire framework was suspended at a depth of 

 15 millims. below the surface of the water; and upon this was 

 laid an india-rubber bag filled with ice, for the purpose of 

 cooling the superficial water (fig. 2). Immediately there was 

 produced a movement of the water passing downwards upon 

 the slope. If a Tellina, a Scrohicularia, or a Pectinaria 

 threw out mud, this was carried downwards with some ve- 

 locity from 10 to 15 millims. ; when the Mollusca and 

 worms creeping about stirred up particles of the surface, the 

 current carried these along with it. At the surface a move- 

 ment of the water towards the cooled spot took place, floating 

 corpuscles went with this, sank down, and glided downwards 

 over the inclined bottom. These movements continued until all 

 the ice was melted, although during this period the difference 

 between the superficial and bottom strata of water amounted 

 only toi°R. ( = P-125F.). 



On the thirteenth day the surface was cooled a second time 

 in the vicinity of the shore. 



On the sixteenth day the lower boundary of the slope had 

 advanced in one place 10 millims., in another 20 millims. ; 

 its inward curve was entirely filled up ; its angle of inclina- 

 tion amounted to 17° above and only to 15° below. On the 

 horizontal bottom the fine organic mass lay to a thickness of 

 3 or 4 miUims. This diffusion of the organic mass was fol- 

 lowed by worms and Mollusca; and Infusoria swarmed at the 

 bottom. 



