192 FRESHWATER RHIZOPODS OF NORTH AMERICA. 



have thousands of these animals now living in midwinter." The description 

 is accompanied with many woodcuts representing various changes of form 

 and conditions of the animal. 



Professor Bailey remarks: "If the reader will imagine a bag made of 

 some soft extensible material so thin as to be transparent like glass, so soft as 

 to yield readily by extension when subjected to internal pressure, and so 

 small as to be microscopic; this bag filled with particles of sand, shells of 

 diatoms, portions of alga? or desmids, and with fragments of variously 

 colored cotton, woolen, and linen fibres, will give a picture of the animal ; 

 to complete which it is only necessary to add a few loose strings to the bag, 

 to represent the variable radiant processes which it possesses around the 

 mouth." 



In the normal condition the animal appears to be compressed obcordate 

 or pyriform, with the filamentous branching pseudopods projecting from the 

 broader extremity. The animals observed by Professor Bailey were in a 

 very active condition, and they are described and figured as gorged with a 

 variety of food. Many are represented in different states of distortion due 

 to the materials swallowed being so much longer than the usual length of 

 the animal. A number of the figures further represent the creature either 

 in the state of conjugation or of division, in which process from a pair to 

 as many as five individuals are engaged together. Professor Bailey refers 

 to the condition as probably being one of spontaneous fission, though he 

 says he did not see it actually occur. Single undistorted individuals appear 

 to have been about 0.1 mm. in length. One is represented extended on a 

 swallowed fibre reaching the length of 0.25 mm. Another is represented 

 in which a swallowed fibre, in the extension of the animal, has perforated 

 the fundus. 



Hertwig and Lesser, in their recent admirable researches, have de- 

 scribed, as it seems to me, the same animal as the Pamphagus mutabilis, under 

 the name of Plagiophrys scutiformis. 



I have repeatedly, though rarely, observed specimens of what I have 

 considered to be the Pamphagus mutabilis of Professor Bailey, but usually iso- 

 lated, and never in anything like the number and variety described by the 

 latter. Those I have met with presented some variety in size, proportions, 

 and shape, but I have viewed them as pertaining to the same. I have 

 adopted Professor Bailey's name of Pamphagus mutabilis, as this was pre- 



