fe) ZOOLOGY 
tinction between the endoplasm and ectoplasm found in these 
and other Gymnomyxa is more apparent than real, and depends 
only on the presence or absence of food and other granules, 
the actual protoplasm of the organism being of one consistency. 
Some of the Lobosa have acquired the power of forming shells, 
and this affords a convenient character by which we can divide 
the class into two orders: (1) the Nuda, and (2) the Testacea. 
Order 1. Nuda—The most familiar example of the 
former order is the Amoeba, of which there are many species 
quite distinct from the amoeboid spores of the Myxomycetes, 
which are often taken for Amoebae. The various species differ 
one from another in the nature of their pseudopodia and in the 
character of their nuclei. In some species the former are little 
more than low eminences, standing out from the general 
surface, in others they are long finger-shaped processes which 
stream rapidly hither and thither. Some members of this 
order, as the Amoeba princeps and Pelomyxa, have numerous 
nuclei scattered through the body: in the first-mentioned form 
these arise by the gradual “fragmentation” of the original 
nucleus. Such a multinucleated condition is constant in some 
species. In some cases the soft protoplasmic body has been 
observed to contract away from, and to lie within, a very thin 
cuticular membrane, which maintains the outline that the 
Amoeba possessed the moment before contracting; this cuticle 
is not usually visible, except in Lithamoeba, when it exists it 
must be very attenuated and elastic. 
Pelomyxa is one of the largest of the Lobosa, the species P. 
palustris having a diameter of more than 2 mm. The external 
protoplasm is clear and produced into pseudopodia (Fig. 3). 
The inner mass is crowded with vacuoles, and contains in addi- 
tion to the numerous nuclei (5, Fig. 3) a number of refringent 
bodies of unknown function (6, Fig. 5),and many food particles. 
It has been observed to set free minute amoeboid spores, which 
probably grow into new Pelomyxas. 
Order 2. Testacea.—The shell which encloses the proto- 
plasmic body of these Lobosa may be soft and cuticular, and 
may then be strengthened by grains of sand adhering to it, or 
it may be hard. In either case the protoplasm can be extruded 
from an aperture in the shell. Arcella (Fig. 4) is a common 
