Sahani 
ao ae 


1891.] _ Rocky Mountain Rhizopods. 1077 
. ever, these particles were present in such abundance that they 
built up the greater part of the envelope and took the place of 
the protoplasmic globules, which were then only few in number. 
The pseudopodia were mostly much elongated,—four or five times 
as long as the diameter of the animal, or more,—very slender, and 
gradually tapering from the base to the summit, which was fili- 
form. They were straight, rigid, few in number (about half a 
dozen), and were capable of radiating in every direction, while the 
animal walked on their points. At other times the animal would 
crawl along the grounds, slightly compressed at its point of con- 
tact, and then the pseudopodia would be shorter, less rigid, and 
flattened. 
The nucleus and the éontfactile vacuole could not be seen, 
being hidden behind the envelope of globules. In short, this spe- 
cies recalled very much the Am@ba radiosa, from which it was 
distinguished by its constant protective envelope, as well as by its 
very much smaller size. 
Having in the preceding pages given a description of the 
Rhizopods I found in the Rocky Mountains, I should like to 
present a few general remarks on the structure of the shell in these 
animals. 
These organisms have sometimes been divided into “ Nuda” 
and “ Testacea.” There exist some transitional species, whose 
plasma is simply hardened on most of its surface, or covered with 
protective granules, or is even differentiated into a genuine ~ 
double-contoured, supplg, and membranous covering. But in 
what follows I shall only treat of the true “ Testacea,” with a solid 
and rigid shell. The Testacea constitute by far the greater part 
of fresh-water Rhizopods. : 
The nature of the shell in these beings is as yet little known. 
Generally speaking, and after consulting most of the works that 
have been written on these animals, one arrives at the following 
conclusion: The shell of the fresh-water Rhizopods is chitinoid, 
- often with an admixture, in various proportions, of siliceous ele- 
ments (sand grains, diatoms, scales). 
My observations, which have been made on nearly all the 
known species, allow me to modify the preceding opinion, and to 
