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an actual approach and fusion. In, either event, the case in 
question is of interest since it emphasizes the fact that the 
smooth and pitted shells of Arcella are merely varieties of the 
same species. The interchange of protoplasm between the shells 
was active, the direction of flow reversing seven times in eight 
minutes. Height of one shell 44 microns. 
^Unknown rhizopod. 8 to 11, figure 53. 
A single specimen of this large and sluggish rhizopod was 
under observation an entire afternoon, hut its unusual trans- 
parency and a cloudy day combined against the observer. When 
it was revolved, the body was seen to be shaped like a football 
with a few long, firm pseudopodia, the periphery and center 
being finely granular with a space or clear plasm lying between. 
No mouth, nucleus, or vacuole were apparent, and when elec- 
tric light was finally thrown in it was fatal to the specimen. 
Size 200 microns. 
* Euglypha mucronata Leidy. 14, figure 53. 
Shell cylindrical, tapering toward the mouth, transparent, 
composed of circular imbricating plates which later become al- 
most homogeneous. Pseudopodia delicate and geniculate. This 
form is similar to the common Euglypha alveolata Duj.. but 
with the fundus prolonged into an acute tip. 
Class II Actinopoda 
Actinoplirys sol Ehr. 12 and 13, figure 53. 
This is another form almost too common to mention except 
when especially favorable conditions bring out some interesting 
phase or mechanism. The contractile vacuole in this species is 
a permanently thin place in the peripheral plasm or membrane 
which upon collapse falls into folds and gives the appearance 
of a tuft of hairs. Figure 12 shows the stages of slow refilling 
and sudden collapse. Average time of action forty seconds. 
xlOOO. 
1* Nuclmria delicatula Cienk. 15 to 22, figure 54. 
Body both amoeboid and lieliozoan-like, with pseudopodia in 
turn amoeboid, short and spicule-like, long and raylike, deli- 
cate and intricately branched, .capitate (rarely) but not suc- 
torial, stocky for attachment, and anastomosing in at least one 
instance under observation. Length of body 20 to 100 microns. 
Maximum extent of pseudopodia 315 microns. 
