186 FRESH-WATEE EHIZOFODS OF NOETH AMERICA. 



pale granular, colorless, or faintly yellowish ball, invested with a colorless 

 membrane seen at the border as a distinctly double contour-line. When 

 the creature begins to move, a clear, delicate, transparent zone is seen to 

 extend from the body on one or another side or all around 



An attentive study of Cochliopodium in its various movements indi- 

 cates the animal to be bell-shaped, with a flexible shell, which it is capable 

 of widely expanding at the mouth. At the fundus and sides, the membrane 

 is comparatively thick, and is observed at the borders as a double contour- 

 line. The lower part of the shell is exceedingly thin and delicate, and 

 may be inflected or more or less widely reflected, the mouth contracting 

 or enlarging proportionately with the inflection and reflection of the part 

 of the shell surrounding it. The interior sarcode is continuous with its 

 chitinoid membranous investment, and at no time appears to become 

 separated so as to leave spaces filled with water, as in Hyalosphenia 

 or Euglypha. 



Cochliopodium in form may be compared with an Arcella, and the 

 shell of this would be like that of the former, if its basal portion were very 

 thin and capable of reflection beyond the border of the base. 



The broad zone surrounding Cochliopodium, as seen in figs. 1, 16, 17, 

 21-23, in the upper or under view of specimens, or the broad crescentic 

 band spreading more or less on one side in corresponding views, as seen in 

 figs. 2-4, 12, In, 19, are due to the reflection or turning outwardly of the 

 thin basal band of the shell surrounding the mouth. In the lateral view of 

 specimens, the same band may be likewise observed more or less reflected, 

 as seen in figs. 5-9, 11, 18, 20. When the thin basal band is closed or 

 completely inflected, specimens appear as in figs. 13, 14. 



In the maturer specimens of Cochliopodium, the shell exhibits a punc- 

 tate appearance, due to a minutely cancellated structure, probably like that 

 of the shell of Arcella. The structure is especially to be detected in the 

 double contour-line seen bordering the body, and in the basal band of the 

 shell. In the intermediate position it is obscured by the granular structure 

 of the sarcode. The punctated structure is sometimes exceedingly indis- 

 tinct, and can be detected only under the best defining power of the micro- 

 scope, together with the most favorable disposition of light. In young 

 specimens, as in those represented in figs. 21-23, I could detect no evi- 

 dence of the cancellated structure, and infer that it is developed only at a 

 later period. 



