40 



THE HISTORY OF ECOLOGY 



which have been formed in very deep vi^aters. 

 If this be so, we shall have to admit that the 

 areas now respectively occupied by our conti- 

 nents, as circumscribed by the two hundred 

 fathom curve or thereabout, and the oceans, 

 at greater depth, have from the beginning 

 retained their relative outhne and position; 

 the continents having at aU times been areas 

 of gradual upheaval with comparatively shght 

 oscillations of rise and subsidence, and the 

 oceans at aU times areas of gradual depres- 

 sion with equally shght oscillations." 



Alexander Agassiz, son of Louis, is much 

 more closely identified with oceanographic 

 expeditions and with oceanography in gen- 

 eral than is his more famous father. His 

 work is associated with the cruises of the 

 Blake and the Albatross. His active con- 

 nection with oceanography extended from 

 1877 to 1905 and included both general 

 exploration by dredges and nets and much 

 study of the coral reef problem. The con- 

 clusions reached by Alexander Agassiz con- 

 cerning the origin of coral reefs were di- 

 rectly opposed to the subsidence theory of 

 Charles Darwin. After a great deal of 

 search, the younger Agassiz could not find 

 an atoll or barrier reef the formation of 

 which, he thought, could be adequately 

 explained by Darwin's subsidence theory. 

 He also concluded as a result of extensive 

 dredging that the benthic animals of the 

 Caribbean Sea are more closely related to 

 the deep-sea animals of the Gulf of Panama 

 than to those of the deep Atlantic, a con- 

 clusion that has stood the test of time to 

 date. His book (1888) deserves especial 

 mention. 



As a result of working with a tow net 

 that could be opened and closed under 

 water at any depth, Alexander Agassiz 

 modified somewhat the old idea of an azoic 

 depth zone. He thought that there were 

 practically no plankton organisms in the 

 vast intermediate waters of the ocean below 

 a depth of about 200 fathoms until one 

 came near the bottom. Murray and others 

 disagreed, and on this note of friendly dif- 

 ference of opinion the nineteenth century 

 closed with the azoic zone problem consid- 

 erably modified, but still alive. We may 

 properly overstep the time limit for the 

 present chapter and bring this particular 

 matter down to 1934 by a quotation from 

 Krogh (p. 430) : 



"The number and total mass of organisms 

 decreases very rapidly with the depth. This has 



been estabhshed again and again both for net- 

 plankton and for nannoplankton organisms and 

 is well illustrated by the figures given by 

 Hentschel for the number of nannoplankton 

 organisms present in 1 liter of ocean water in 

 the area 0-10° S and 10-20° W in the At- 

 lantic: Surface, 10,100; 50m., 9400; 100m., 

 2700; 400m., 260; 1000m., 90; 2000m., 50; 

 3000m., 18; 5000m., 15." 



While the plankton population is much re- 

 duced, there is no completely azoic region 

 indicated by these data. 



Herdman (1923, p. Ill) quotes John 

 Murray's estimate of Alexander Agassiz's 

 influence on oceanography as follows: 



"If we can say that we now know the 

 physical and biological conditions of the great 

 ocean basins in their broad general outhne— and 

 I believe we can do so— the present state of our 

 knowledge is due to the combined work and 

 observations of a great many men belonging to 

 many nationalities, but most probably more 

 to the work and inspiration of Alexander 

 Agassiz than to any other single man." 



This estimate, which has the approval of 

 two excellent students of the subject, may 

 help rescue the son from the comparative 

 obscurity produced by the shadow of his 

 father. Alexander Agassiz's last studies and 

 his last expedition in the Albatross came in 

 the early years of the present century; 

 hence we have reached the end of the 

 period to be covered in the present chapter. 

 The ecological problems of the ocean had 

 been outlined before 1900, and many of 

 them were well advanced toward solution. 

 With some notable exceptions, such as 

 Mobius' recognition of the oyster bed as a 

 biocoenosis, the possible ecological impHca- 

 tions of these studies had not been 

 emphasized. 



LIMNOLOGY* 



The development of limnology lagged be- 

 hind that of oceanography, as shown by 

 the fact that Forel (1892), in the first vol- 

 ume of his monograph on Le Leman (Lake 

 Geneva, Switzerland), defined hmnology 

 as the oceanography of lakes. Despite much 

 good work on the taxonomy and natural 

 history of fresh-water organisms, it re- 

 mained for P. E. Miiller (1870), a Dane, 

 to recognize the existence of a pelagic 

 planktonic fauna in lakes, such as Lilljeborg 



• Short historical sketches of limnology are 

 given by Lampert (1910) and Welch (1935). 



