LIFE IN THE OCEAN. 503 



necessary to estimate the number of individuals of each sort. Although 

 this counting involves great expenditure of time, it is quite indispen- 

 sable to the ascertainment of the production. It is necessar3\ i" tat't, 

 to separate the producers from the consumers. It is proper, also, to 

 take into account, at least for the principal species, the rapidit}^ of 

 increase, the duration of the different stages of development under 

 the various conditions of life, the mode of alimentation and the needs 

 of the principal animals. The results of the drafts taken at the begin- 

 ning of the year may be regarded as a principal sum of money, of which 

 the interest is spent in the course of the year, the capital remaining at 

 the end about what it was at the beginning. The comparison of the 

 quantities of animals of each sort and size in the successive drafts, 

 together with the knowledge acquired by direct observations of their 

 alimentary needs, enable us to infer whether the consumption is really 

 sufficient to absorb the annual vegetable production. This comparison 

 requires a very large set of drafts, because the rate of augmentation 

 of the different species depends upon the conditions of life, and con- 

 sequently varies from one season to another. Finally, the chemical 

 analysis of the principal plants is necessar}^ if we wish to compare the 

 productivit}^ of the sea in organic matters with that of the land. 



It has been questioned whether it is possible to acquire an exact 

 notion of the production of a part of the sea by observations of the 

 plankton alone. But the objections which have been made neglect the 

 fact that under natural conditions a body of sea alwaj^s produces as 

 much as possible, and that in a small body, like the Kieler Bucht, for 

 example, the production in the middle of the water, and even along 

 the coasts out of the light — a production which is the same for the 

 whole surface — depends essentially upon the nutritive matters that 

 the plants find in solution in the water. But in consequence of the 

 incessant stirring up and mixing of the water, there can be no sensible 

 difference between the nutritive matters which are presented to the 

 plants in the open sea and in inshore places. Consequently the atten- 

 tive observation of the plankton taken up, as has been said, in a par- 

 ticular place during a whole year, furnishes a sufficiently accurate 

 scale of comparison for an estimate of the capacity of production of 

 the whole body considered, whether the production inshore is a little 

 less or a little more than that of the open sea. 



Thus far, the method of the quantitive examination of the plankton 

 has been applied to the following marine bodies: 



First. In shoal water: 



(a) During several years: The Kieler Bucht (possibly the Kieler 

 Hafen is meant). 



(h) During all seasons of one year: 



In the Arctic zone, the Fjord of Karajak, in Greenland, in latitude 

 70° N., by Vanhoeffen. 



