918 
bodies which constitute one-third or more of the central mass of the 
amoeba. Their shape varies from the perfectly sharp-pointed spinous 
type of Celli and Fiocca to a very broad, flat, oval, or even to a narrow, 
undulating type, which may run around the surface of the amceba, having 
very much the appearance of the undulating membrane of a monad, just 
prior to its encystment. 
The number of pseudopodia which may be present on an amoeba at 
any one time may vary from one to five or more, and frequently pseudo- 
podia pertaining to a pseudopod may be seen. 
Whatever the type or the number of pseudopodia may be, their general 
structure and contents vary but little. The outer coating is formed by 
the ectosare, and the contents consist of a portion of the fluids of the 
parasite alone, to which, as the projection grows larger, may be added 
portions of the endosare, and sometimes vacuoles, foreign bodies, etc., 
and, very rarely, the nucleus of the amceba. In some instances, the 
endosare follows the ectosare in its protrusion so closely that a line of 
demarcation can not be distinguished and, indeed, it may seem as if the 
ectosare was being pushed out by the endosare. 
One very important point, which we have not seen noted elsewhere, 
is the change in the elasticity of the ectosarc itself during the formation 
of the pseudopod. The portion of this organ which covers the pseudopod 
is often much thinner and correspondingly denser than it is in other 
places, and with very large pseudopodia or where several are present, 
this stretching of the ectosarc may be sufficient to increase considerably 
the linear measurements of the surface of the ameeba itself. 
This fact may be brought out quite distinctly by staining the moving 
amoeba with a very dilute solution of neutral red, which sharpens the 
distinction between ectoplasm and endoplasm, without in any way interfer- 
ing with the motility of the parasite. This phoenomenon may also be 
confirmed by a study of parasites which have been quickly fixed and 
stained with their pseudopodia well formed. 
The character of the pseudopodia varies just as much in cultures of 
pure species of amcebe as it does in those which are not pure. One of 
our first amcebe obtained in culture, while showing only lobose pseudo- 
podia in the stool from which it came, when it was first grown on 
artificial media developed perfect, spinous pseudopods, and later would 
at times develop the spinous and again the lobose type. In the intes- 
tinal contents of animals inoculated with it, only lobose pseudopodia 
were observed, but in subcutaneous abcesses produced by inoculation of 
similar cultures the spinous variety was frequently present. 
(b) Ectoplasm.—This elastic structure surrounds the outer portion of 
the amceba. It varies in thickness from about one-third of the diameter 
of the parasite to a very thin streak, almost a line. Its distinctive 
appearance is probably only completely developed in the full-grown 
parasite. 
fe eee” ere S. 
