178 
POPULAR SCIENCE REVIEW. 
Notliing ill the study of these objects has proved more 
perplexing than the attempt to separate them into specific 
groups. Observers who_, like D^Orbigny_, merely selected a 
few prominent varieties^ found no difiiculties. They assigned 
to such types generic and specific names with a recklessness 
that was as unphilosophical as it was perplexing to those who 
followed them. When studying the British forms of Lagense^ 
in 1847^ I became satisfied that the old specific divisions were 
unsatisfactory. It was obvious that my predecessors had 
wholly misunderstood these objects^ from their ignorance 
of the immense range of variation that each species was 
capable. But bold as many fellow-labourers deemed my 
innovations_, they fell far short of what my subsequent inquiries, 
and those of Dr. Carpenter, Professor Pupert Jones, and 
Mr. Parker, have shoivn to be necessary. Consequently, in my 
memoir on the British Foraminifera I stated, that the hard 
shells of the Foraminifera do not constitute a sufficiently 
constant and important element in their organization to justify 
our trusting to them as guides in the discrimination of species 
a conclusion that the elaborate inquiries of Messrs. Parker 
and Jones have done much to confirm. At present we can do 
little more than recognize what appear to be certain typical 
forms around which variable groups may be gathered; but 
even here we become involved in serious difficulties, since the 
various groups pass so gradually into each other that their 
boundaries become most uncertain; besides which, it will 
often remain a mere opinion what forms are to be regarded as 
the types and what the subordinate members of a group. 
There is abundant room for arbitrary selection on this as on 
every similar point connected with the classification of these 
obscure organisms. 
Devoted as this sketch mainly is to the structure and 
physiology of the Foraminifera, little requires to be said re- 
specting their geographical and geological relations. There 
are few parts of the ocean where they do not occur. Their 
dead shells are cast upon our shores. Some living kinds are 
found adhering to the roots of Laminariae but a few feet below 
the low- water mark. They become still finer and more 
abundant as we pass into somewhat deeper waters, beyond 
which the individuals become more numerous, though the 
types become much fewer. This state of things culminates 
in the true habitats of the Glohigerina hulloides, and its 
constant companion, the OrhuUna universa. These two are 
thorough .cosmopolites, being found from pole to pole and 
at every known depth ; but their true home is in some of the 
deepest parts of the ocean, especially where the gulf-stream 
crosses the Atlantic^ and in other similar localities in the 
