HUXLEY, ON CLASSIFICATION. 73 
these creatures, nothing is to be discerned but a mass of jelly, which 
might be represented by a little particle of thin glue. Not that it 
corresponds with the latter in composition, but it has that texture 
and sort of aspect; it is structureless and organless, and without 
definitely formed parts. Nevertheless, it possesses all the essential 
properties and characters of vitality ; it is produced from a body like 
itself; it is capable of assimilating nourishment, and of exerting 
movements. Nay, more, it can produce a shell; a structure, in 
many cases, of extraordinary complexity and most singular beauty 
(Fig. 2, D). 
That this particle of jelly is capable of combining physical forces 
in such a manner as to give rise to those exquisite and almost mathe- 
matically-arranged structures—heing itself structureless and without 
permanent distinction or separation of parts—is, to my mind, a fact 
of the profoundest significance. 
Though a Rhizopod is not permanently organized, however, it can 
hardly be said to be devoid of organs; for the name of the group is 
derived from the power which these animals possess of throwing out 
processes of their substance, which are called “ pseudopodia,” and 
are sometimes very slender and of great length (Fig. 2, E), sometimes 
broad and lobe-like (Fig. 2, A). These processes may flow into one 
another, so as to form a network, and they may, commonly, be thrust 
out from any part of the body and retracted into it again. 
If you watch one of these animals alive, you see it thrusting out, 
first one and then another of its pseudopodia, exhibiting changes of 
form comparable to those which the colourless corpuscles of the 
human blood present. The movements of these Rhizopods are quite 
of the same character, only they are much more extensive and effect 
locomotion. The creature also feeds itself by means of its pseudo- 
podia, which attach themselves to nutritive particles, and then draw 
them into the substance of the body. There is neither ingestive nor 
egestive aperture, neither special motor nor prehensile organs, but 
the pseudopodia perform each function as it may be required. 
But here, again, we labour under an imperfection of knowledge. 
For, although it is quite certain that the Rhizopoda may multiply by 
division of their substance—in a way somewhat analogous to that 
which I detailed when speaking of the Gregarinida—yet, as in that 
case, we have no knowledge of any true sexual process. It is a most 
remarkable circumstance that though these animals are abundant, 
and are constantly under observation, we are still in doubt upon that 
essential point,—still uncertain whether there may not be some phase 
in the cycle of vital phenomena of the Rhizopoda with which we are 
unacquainted ; and, under these circumstances, a perfect definition of 
the class cannot even be attempted. 
