134 FEESH-WATEE EHIZOPODS OP NOETH AMEEIOA. 



The sarcode of Myalosphenia papilio I have never seen entirely filling 

 the shell. Its proportionate size with the capacity of the latter varies very 

 much, the difierence apparently being more or less dependent upon the 

 amount of nutriment taken by the animal. Thus I have observed, in the 

 summer months, when apparently the conditions* of life were most favor- 

 able to the animal, that the sarcode mass was largest, and most nearly filled 

 the shell, as seen in fig. 1. Under less favorable circumstances the sarcode 

 was smaller ; and sometimes the animal would impress me with the idea of 

 being starved, when the sarcode mass would occupy less than half the 

 capacity of the shell, as seen in fig. 4 



In the view of the broad surface of H. papilio, the sarcode mass usually 

 appears pouch-like in outline. The upper part is ovoid; the lower part is 

 as wide as the shell contiguous to the mouth, and the intermediate part is 

 contracted. In the view of the narrow side of the animal, the sarcode 

 mass touches the shell laterally, and appears therefore to fill it more in the 

 less than in the greater breadth. 



Diverging processes of the ectosarc fix the sarcode mass to the sides 

 and fundus of the shell. These processes, of course, vary in length in 

 proportion as the sarcode mass diminishes or increases. They are conical 

 extensions of the ectosarc, more or less tapering to filaments, and are 

 usually simple, but sometimes furcate at their outer connection. They are 

 of the nature of pseudopods, and may be detached from the shell and 

 withdrawn into the sarcode mass, while new ones may be projected and 

 extended to become attached to the shell. 



The sarcode of H. papilio is remarkable for the quantity of chlorophyl 

 which enters into its constitution. I have never met with a living speci- 

 men of the animal in which this material was absent. It is of a bright 

 green color, like that of the green fresh-water polyp Hydra viridis, and 

 occurs in spherical corpuscles ranging from j^„th to the JLth of an inch in 

 diameter. They are usually so numerous as to obscure all the other con- 

 stituents of the sarcode; but almost invariably this is free from them in 

 the vicinity of the mouth. . 



The basis of the sarcode is the usual faintly granular coloriess proto- 

 plasm mingled with larger and more distinct granules. The ectosarc every- 

 where appears coloriess and clear or faintly granular. 



The interior of the sarcode mass near the upper part is occupied cen- 



