MODERN BIOLOGY 559 



while fresh fields have been opened up for the employment of their methods 

 on an extensive scale. Among these novel spheres we note not only new 

 land-areas — it was not until our own period that the entire globe can 

 be said to have been explored and described — but also to a still greater 

 degree the oceans, the deeper areas of which have only recently been known 

 as regards their physical character and conditions of life. Our knowledge of 

 them has been gained partly through the work carried out at the zoological 

 marine stations, of which the most famous in recent times has been that 

 founded by Anton Dohrn (i 840-1 909) at Naples, and partly as the result 

 of oceanographic expeditions specially equipped for the purpose, among 

 which may be recalled in particular the important English Challenger expedi- 

 tion (i 872.-6) and the German Valdivia expedition (1898-9), not to mention 

 the results obtained by polar expeditions equipped by a number of countries, 

 both large and small. It is through these voyages of exploration that the 

 life-forms of the ocean first became known — the life in the vast depths, 

 whose denizens live in constant darkness and under high pressure and of- 

 ten assume amazing forms; the actual inhabitants of the vast ocean-expanses, 

 the so-called plankton fauna and flora, with their often transparent and frag- 

 ile forms, which are constantly swimming in the water, forms of widely 

 differing systematic groups; and, lastly, the life that moves around the coasts. 

 Innumerable workers have devoted themselves to this branch of study, which 

 has often been carried out under the leadership of committees, national and 

 international, with the consequence that the work and its results have to 

 a certain extent acquired an impersonal character. The pioneer in this field 

 is Karl August Mobius (1815-1908), professor first at Kiel and then in 

 Berlin. By his great work Die Fauna der Kieler Bticht (1865) he has created 

 the modern system and methodics of oecology. By way of introduction he 

 describes the topography of the estuary that he investigated, various sec- 

 tions of it being surveyed and characterized in regard to position, depth, 

 and their plant and animal life. He then presents in systematical order the 

 creatures that inhabit each locality. Others have continued along the path 

 thus beaten by Mobius. Among them may be named Victor Hensen (1835- 

 1914), who was professor of physiology at Kiel and in that capacity studied 

 the structure of the auditory organ, but afterwards he devoted himself en- 

 tirely to marine research, chiefly with the idea of improving the fishing 

 industry. He made a special study of plankton life, with particular refer- 

 ence to its microscopical forms. In order to advance the study of these crea- 

 tures, which are of importance as food for fish, he worked out a statistical 

 method of his own. Of others who laboured in this sphere, to some extent 

 practically important, may be cited the Dane C. G. J. Petersen (born in 

 i860), who investigated animal life in the sounds and bays of Denmark on 

 a method of his own, and J. Schmidt (born in 1877), who after lengthy and 



