226 Hazen: Lire HISTORY oF SPHAERELLA LACUSTRIS 
one attached, each part being invested with a cellulose membrane. 
Probably the premature rupture in this case was due to the pres- 
sure of the cover-glass; the double zooid, however, was vigorous 
enough to swim about actively after more water was supplied. 
Very frequently dumb-bell shaped pairs are found which are ciliated 
at both ends (Fig. 40) and which do not fuse but sometimes do 
succeed in becoming separate. More rarely three- or four-headed 
monstrosities of a similar nature are found (Fig. 41). 
Velten said that these conjugating pairs were always to be 
found in glass vessels placed in sunlight. I have found these mal- 
formations more abundant under such conditions, but sometimes 
also even in darkened cultures. 
THE ALLEGED AMOEBOID CONDITION 
White (’80) has described what he thought might be the trans- 
formation of Sphaerella (Protococcus pluvialis) into an amoeboid 
condition. He found amoeboid organisms containing in the center 
a colored mass like that of Sphaerella, and he supposed that “ the 
structureless envelope becomes the homogeneous part of the 
Amoeba while the granular center becomes the granular Am- 
oeba.” He says further, “ I have to-day seen an Amoeba with 
a well-defined homogeneous circular zone having within it a pale 
green area with the red oil spot but to one side rather than cen- 
trally situated, evidently a Protococcus undergoing change to 
an Amoeba. Now the well-defined circle has broken up into the 
usual amoeboid projections and it has passed beneath some de- 
cayed vegetation and become invisible." 
Dangeard (88) discredits this amoeboid state, and there can be 
little doubt that it represents the case of an Amoeba digesting a 
zooid of Sphaerella. I have several times found such cases. I 
once observed a rhizopod (Actinophrys) devour eight megazooids 
in a short time; the green pigment was quickly digested, the red . 
more slowly. : 
SrEciaL MogPHOLOGY or Mtrcazooips.—THE CELL-WALL AND 
SHEATHS OF CILIA 
The cellulose character of the cell-wall was doubted by Busk 
(53). Cohn (’52), however, states positively that he succeeded in 
