1^16] Introduction iii 



elusions respecting the relations maintained between marine organisms 

 and the hydrographie elements of their environmental complexes. 

 Such information, greatly restricted because of incompleteness of data, 

 is given by Dr. McEwen in his "Sununary and Interpretation of the 

 Hydrographie Observations made by the Scripps Institution," the 

 last paper in this volume. 



What justification has the biologist for his deep interest in hydro- 

 graphic matters? To be sure, they concern the conditions under 

 which marine organisms live, but is such intensive investigation funda- 

 mentally valuable and necessary to the biologist? Cannot all essential 

 knowledge concerning the relation between marine organisms and 

 their environments be ascertained as accurately and much more ex- 

 peditiously by subjecting a few typical organisms to carefully con- 

 trolled laboratory experiments? Such are some of the questions con- 

 tinually being asked, and the primary purpose of this paper is to 

 inquire into their significance. 



The first step in this inquiry consists in distinguishing between 

 marine biology and general biology. To discuss completely all the 

 implications involved in this distinction would require more space than 

 this paper permits. They have been pointed out over and over again 

 by the Institution 's director, to whom I am indebted for many valuable 

 suggestions. The time seems opportune, however, for assembling cer- 

 tain facts revealed by my own research which support these implica- 

 tions and for combining them into an organic whole, to the end that 

 some of the too prevalent misconceptions concerning the nature and 

 function of marine biologv may be corrected. 



2. Marine Biology vs. Gener.vl Biology 



To understand marine organisms is obviously the function of 

 marine biology. To \vhat extent and why do marine organisms differ 

 in structure, function, and behavior from land and fresh-water 

 organisms, and how did these diiferences arise? In short, by virtue 

 of wliat is a marine organism marine? This is the central question of 

 marine biology: all others are strictly tributary to it. Possession of 

 gills, swim-bladders, fins, webbed feet, etc., adapts animals, morpho- 

 logically, to an aquatic but not necessarily to a marine habitat. The 

 fundamental problems of morphology and cytology, regarded as 

 branches of marine biology, are therefore contained in these questions : 

 What are the niceties in structure which adapt marine animals and 



