the Animals of the Deep Seas. 



1!»7 



6 centinis. lii^li ; tli;it ut" the laii^cr one (fig. 2) 53 centims. 

 long, 2.S cciitiiiis. liioail, ami IG centims. higli. The two 

 larger perpemlieular walls were glass plates*. 



l-itr. 1. 



Surface ofWattr 



--.& 



.■^oyrif^ :-:4^:^^lctT:^;v^--^;a^^^>:^v---v:'tw^'^v. 



The bottom of the smaller aquarium, after it had hccn filled 

 with water, Avas covered with a thin layer of sand, to which I 

 gave an inclination of about 5° (fig. 1). I then, by means of 

 a s])Oon, allowed fine mud-])artick's, which had been sifted out 

 of the mud of the mud-region of the harbour of Ki(.d, to sink 

 slowly dow^n upon one of the narrower sides of the a(iuarium, 

 until a slope of 35-40° liad been formed. The hcapcd-up 

 mass was inhabited by a number of small animals. Gammarus 

 locustttj Cuma Rathkii, Jn'ra albifrons, Scoloplos armiger^ 

 Xemertes gesserensis, Monocelis agilis, Pontoiimax capitattiSy 

 Corhula gibbciy Tellina balfhica, and Scrobicularia alba soon 

 made themselves visible in the superficial layer. The next 

 day the mass had settled a little, and its lower boundaiy had 

 already perceptibly advanced. On the third day its progress 

 was already 3 centims. I now laid a few spoonfuls of sand 

 upon the uppermost part of the slope, and then disturbed the 

 equilibrium of the Avatcr for a few minutes by moving a finger 

 up and down in it. By this means the abruptly rising sand 

 acqiiired a more oblique direction, and covered the mass of 

 mud for a breadth of several centimetres. Two days later, 

 this sand had for the most part sunk down into the mass of 

 mud and pushed it still further forward even at the bottom. 

 Its angle of inclination had decreased from 35-40° (its original 

 amount) to 25°, and the sand spi-ead over the horizontal bot- 

 tom was covered throughout with fine mud-particles (fig. 1, 

 line a, b, c). 



" The two figures represent profiles of these aquaria. The Jotted Hue 

 indicates the future surface of the organic mass. In fig. 2 tlie arrows 

 indicate the direction of the sinking current. 



