Vou. 2] Ritter—Introduction. XV 
to the present state of this domain of science ; and in what particu- 
lars, if any, Nature has given us opportunities to be of special 
use in advancing it. Looking over the whole domain, one sees 
that while certain geographical regions, like the Mediterranean, 
the North and Baltie Seas, the environs of the British Islands, 
and, to a less extent, the North American half of the Atlantic, 
have been cultivated, intensely even, in certain particulars, when 
attention is directed to large problems rather than to space areas, 
the thoroughly subjugated portions are exceedingly small. 
Let one go to the Bay of Naples, for instance, perhaps the 
best cultivated locality, and make inquiry about the ecology of 
the most familiar species found there, and see how far from satis- 
factory an answer can be obtained. In the realm of pelagic life, 
no one would contend that the great expeditions of the last half- 
century, even that of the Challenger, of the Blake, and the recent 
more concentrated and betted equipped German Plankton and 
Valdivia Expeditions, and those of the Albatross, have done more 
than to effect a reconnoissance of the field. The most general ques- 
tions of seasonal, vertical, and areal distribution are still topics of 
widest divergence of view, and of lively discussion; and it is 
obvious that this diversity is in large measure due to the 
mere matter of dearth of readily ascertainable information. 
Beyond the most general truth, important is this is, that the 
bottom of the sea, even in its deeper parts, is inhabited by ani- 
mals, how immediately one comes against a blank wall when he 
begins to ask questions about this life. How abundant is it? 
Does it actually reach into the profoundest depths? Are we to 
suppose it to be uniformly distributed over the entire ocean floor, 
modified only by local conditions, or as belonging essentially to 
the continental margins, with only an advance guard of strag- 
glers, so to speak, reaching to the localities farthest removed 
from any land? How long, geologically, have the truly abyssal 
depths been inhabited, and when and how did they become inhab- 
itable? From what source did the immigrants to these regions 
come? If from the littoral realms, has there been a general 
movement of approximately equal importance from all shores, 
or has it been chiefly from the polar regions? What is the signifi- 
eance, biologically, of the continental shelf? What of Murray’s 
‘‘mud line’’? 
