HYDROTDS. 21 



both organic matter in solution and oxygen ; and that this same water, 

 after having passed through the bodies of these lower forms of animal 

 life, is deprived of both its organic elements and its oxygen. The 

 theoretic difficulty which had determined the problem of life in the 

 depths of the sea was thus removed; for, given this lowest form of 

 animal existence, the higher are always possible. 



The same awful cycle of life, death, decomposition, and life again, 

 which is again and again repeated among the higher organisms, is 

 found working itself out as inexorably in the oceanic depths. The 

 elements which are appropriated from the mighty reservoir of the 

 ocean for the maintenance of the life, are restored to it again by the 

 death, of each organic being. 



The bed of the ocean, from the tiny lakelets left by the retiring 

 tide to the greatest depths ever reached by trawl and dredge, is found 

 to be teeming with exquisite forms of life. Delicate plant-like forms 

 are found clinging to rocks and shells, or spreading themselves over 

 the broad fronds of the algae. Every peculiarity of vegetation is 

 mimicked ; graceful stems rising from tangled roots send out branches 

 which bear raceme-like clusters of buds, and delicate bells whose 

 beauty no words can describe. 



Fig. 5. Roving Medusa of Tubdlaria indivisa. (Magnifled.) 



A hundred and fifty years ago nothing was known of these beauti- 

 ful hydroids. The first investigation deserving the name was made 

 by Abraham Trembley. This man was born in Geneva in the year 

 1700. While residing at the Hague, as tutor to the sons of Count de 

 Bentinck, he made a series of remarkable observations upon the fresh- 

 water hydra. The results of his observations were published first by- 

 Reaumur in 1742, and two years later by himself. In 1727 Peysonnel 

 had paved the way for Trembley by proving the animality of the 

 corals. Jussieu visited the coasts of Normandy to investigate the 

 coral question, after Peysonnel's publication of his views, and there 

 conclusively demonstrated the animality of Tuhularla indivisa, one 



