LIFE IN THE OCEAN. 497 



of view, the differentiation of tlie different kinds of bacteria which take 

 part in the processes of putrefaction in the sea, the stud}^ of their 

 modes of action, conditions of existence, and propagation will be of 

 great interest. 



Besides a general knowledge of the cycle of transformations of mat- 

 ter, we need the knowledge of the composition and transformation of 

 the plants and animals that we have to study and of the action upon 

 them of their environment in order to comprehend the phenomena of 

 nature and to solve the practical questions to w iiich they give rise. 

 It is needful, also, to at least determine the importance of the com- 

 monest species. 



Practical agriculture has gained great benefit from investigations of 

 this sort and from results obtained in regard to the relations which 

 exist between the many factors of the question. 



Advantages have also been derived from man}'^ conquests of science 

 for the utilization of ponds, and it ma}^ be hoped that the same prin- 

 ciples applied to marine matters will lead to a more complete utili- 

 zation of the products of the sea. The object of cultivating the soil is 

 to obtain with the smallest possible expense and least work the greatest 

 product. Efforts tend to augment the fecundity of the soil by such a 

 stud}^ of the causes of that fecundit}' as permits the elimination of 

 harmful influences. In the same way we ought to endeavor to get 

 from the sea the greatest possible quantity of useful products. For 

 that purpose, the first thing to be done is to make an exact inventor}^ of 

 the real product of the ocean, or only of a particular, part of the sea, 

 compared with what is furnished by cultivated soil. This exact knowl- 

 edge of the production gives the surest point of departure not only for 

 a rational exploitation of sea fisheries, but also for a study of the causes 

 of production and of the transformations of matter in the bosom of 

 the ocean. 



There are exact statistics of agriculture. Thus we know that in 

 Germany an acre of meadow yields on the average 1.4 short tons of 

 hay. In order to be able to compare this crop with the product of 

 the same area planted with cereals, or with that of a pond of the same 

 size, we must know the chemical composition of the plants in (jues- 

 tion, so as to be able to compare the different plants, either directly 

 according to their amount of albumen, of fatty matters, etc., or indi- 

 rectly according to their nutritive value, determined by special experi- 

 ments. To ascertain exactly the annual production of flesh per unit 

 of surface is less easy. The most satisfactory method is still that 

 of deducing it from the number of young cattle that can be raised 

 annually upon a suitable area. According to the data collected by 

 Viebahn an acre of cultivated land in Prussia yields 75 pounds of beef 

 per annum. For water, as for land, we can, as Hensen has shown, 



