40 Functions of the Deep-sea Protozoa. \^'fouxZ\%S?i!&\ 
establish is, that in the ' lowest Order of the animal kingdom, and 
in the lowest subdivision of that Order, where differentiation has 
not proceeded beyond a given point and even such indications of 
specialized structure as a definite "nucleus" and "contractile 
vesicle " are altogether absent, nutrition is effected by a vital act 
which enables the organism to extract hydrogen, oxygen, carbon, 
nitrogen, and lime from the surrounding medium, and to convert 
these ingredients into sarcode and shell-material. 
This is, no doubt, in direct opposition to preconceived notions 
of the distinction existing between the Protophyta and Protozoa, but 
I cannot help thinking that, on a closer scrutiny of the grounds 
upon which the distinction is based, it will be found to have its 
foundation in words rather than in established facts ; and that the 
vital attribute now claimed for the lowest Protozoon is, in reality, 
as compatible with reason and observed phenomena as some of the 
other attributes which have been unhesitatingly acceded both to 
the Protozoa and the Protophyta. 
According to Dr. Carpenter, whose well-merited reputation as 
one of the leading physiologists of our time needs no comment of 
mine, "There is reason to consider the shell-substance of the 
Foraminifera as an excretion from the protoplasmic mass of which 
the body itself is composed, just as the cellulose wall of the vege- 
table cell, which may be consolidated by carbonate of lime (as in 
Corallines), or by silex (as in Diatoms), is an excretion from the 
contained endochrome."* But inasmuch as the term " excretion " 
involves vitality ; or, to put the case in other words, since the shell- 
substance would not he excreted were the animal dead, it is obvious 
that the process is, in point of fact, one of secretion, dependent, in 
the first instance, on the creature's power of eliminating carbonic 
acid and hme from the waters it inhabits ; and, in the second, of 
reproducing carbonate of lime in the shape of its shell-substance. 
Unless we admit this explanation, it is difficult to see how we can 
escape the more serious dilemma of having to assume that solid 
atoms of carbonate of lime are merely passed mechanically through 
the animal's body, going in at one side in the shape of solid atoms, 
and coming out at the other in the shape of specially conformed 
shell-tissue. And, be it observed, the same objection holds good as 
regards the process by which the " consolidation " of the cellulose 
wall — by carbonate of lime or silex, as the case may be — takes place 
in the Protophyte. For it is only so long as we consent to be hood- 
winked by a definition which cannot, under any circumstances, be 
accepted as universally applicable, that any doubts can arise as to 
there being a gradual, and not a sudden, transition from the confines 
* "On the Systematic Arrangement of the Rhizopoda," 'Natural History 
Review,' No. 4, October, 1861, p. 472. 
