LIFE AT GREAT DEPTH?. 53 



display a much greater disposition to separate themselves into 

 small families. Thus the number of individuals of the mono- 

 phagous animals depends in a great degree on the nature of 

 their food ; and even the most primitive habit of life, i.e. the 

 instinct of living apart from their fellows, or of living associated 

 in large herds, is very decidedly influenced by it, if not actually 

 produced by it. 



The dependence of the Carnivora on the Herbivora thus 

 clearly indicated, leads to another question that, namely, as to 

 the possibility of animal life existing where no plants can grow, 

 and where consequently no vegetable feeders can live. We 

 know now that, contrary to the opinion which for a 'time 

 prevailed that the bottom of the sea was uninhabitable, a 

 considerable number of the most various creatures live in spots 

 where the sun's rays never penetrate, and where, therefore, no 

 plant can grow. According to Forel, plants containing chloro- 

 phyll cease to be found in the Lake of Geneva at about one 

 hundred fathoms, and the limit in the sea seems to be about 

 the same. Nevertheless, in the Lake of Geneva, which is much 

 more than one hundred fathoms deep, and everywhere on the 

 floor of the deepest Atlantic, we find a multitule of living 

 animals. These, at such great depths, cannot feed on living 

 plants ; they must all be flesh-eaters, as has been confirmed by 

 observation. But as they cannot form organic matter from 

 carbonic acid, water, and ammonia, they must soon infallibly 

 perish if no substitute were provided for the animals destroyed 

 for food. Hence we may be allowed to assume that the organic 

 food found in the plants at the surface of the sea is in some way 

 conveyed to some of them. Professor Mobius of Kiel has 

 lately undertaken the investigation of this problem. He came 

 to the conclusion that the organic matter produced at the 

 surface of the sea by the decomposition of plants and animals is 

 carried down to the bottom by the Sinking Current, as it is called, 

 which results from the difference of temperature at the bottom 

 and at the surface ; this theory, however, cannot be regarded as 

 proved by the experiment which Mobius made for that purpose. 

 In small aquaria which were perfectly protected from any 

 shock, variation in temperature produced sinking currents 



