408 THE DEPTHS OF THE SEA. [CHAP. 1X. 
The remarkable general result that even to these 
ereat depths the fauna is varied and rich in all the 
marine invertebrate groups, has inundated us with 
new material which in several of the larger depart- 
ments it will take years of the labour of specialists 
to work up. While referring very briefly to those 
orders which it has been found impossible as yet to 
overtake, I will enter a little more fully into the 
history of certain restricted groups which more par- 
ticularly illustrate the conditions of the abyssal 
region, and the relations of its special fauna to the 
faunze of other zoological provinces, or to those of 
earlier times. And very prominent among these 
special groups we find the first and simplest of the 
invertebrate sub-kingdoms, the Protozoa, represented 
by three of its classes,—the monera, the rhizopoda, 
and the sponges. 
The monera have been lately defined as a distinct 
class by Professor Ernst Haeckel,! for a vast assem- 
blage of almost formless beings, apparently abso- 
lutely devoid of internal structure, and consisting 
simply of living and moving expansions of jelly-like 
protoplasm ; and although the special character on 
which Haeckel separates them from the remainder of 
the protozoa,—that they are propagated by no form 
of sexual reproduction, but simply by spontaneous 
division,—may probably prove deceptive as our know- 
ledge increases, still their number, their general 
resemblance to one another, presenting obviously 
different and recognizable kinds although with very 
indefinable characters, and the important part which 
* Biologische Studien. Von Dr. Ernst Haeckel, Professor an der 
Universitat Jena. Leipzig, 1870. 
