GENUS HYALOSPHENIA— HYALOSPHENIA ELEGANS. 141 



which appears deeply notched from the turning upward laterally of the 

 oral commissures. 



The shell is composed of transparent chitinoid membrane, of a pale 

 chocolate-brownish hue, without a trace of definite structure. It is of 

 uniform thickness, except that it forms a thicker border to the mouth. 

 The sides of the shell exhibit a more or less symmetrically corrugated 

 appearance, due to series of hemispherical inflections, which are remarkably 

 constant and persistent. 



The mouth is oval, and is convex in its wider diameter. 



The size and form of the shell vary but little. Commonly, specimens 

 range from ith to ~th of an inch in length, ^>th to i th of an inch in 

 breadth, and ^th to * th of an inch thick, with the mouth -i-th of an inch 

 in the greater and ^th of an inch in the less diameter. 



The sarcode of H. elegans is colorless, though sometimes the endosarc 

 appears more or less yellowish from the quantity of food it contains. 

 Usually, the endosarc contains many vacuoles and food-balls, mostly of a 

 yellowish or brownish hue, besides which it contains the usual constituents 

 found in allied forms. 



The nucleus is usually more or less obscixred or may be completely 

 hidden from view by the surrounding materials. It is pale granular and 

 globular, and measures from ..^th to j^th of an inch in diameter. 



From two to four contractile vesicles are frequently visible together in 

 the vicinity of the nucleus at the periphery of the sarcode mass They 

 measure about the ^th of an inch previous to their collapse. 



The mass of sarcode occupies more or less of the interior space of the 

 shell, according as the animal has been well or poorly supplied with nourish- 

 ment. Sometimes it nearly fills the shell; at others, it barely occupies half 

 its capacity. Extensible threads of ectosarc diverge from the sarcode 

 mass to the sides and fundus of the shell, varying in length in proportion 

 as the mass enlarges or diminishes 



The pseudopods are digitate, usually three or four in number, mostly 

 simple, sometimes forking or branching, and finely granular in constitution. 



Specimens of H. elegans are frequently found with the sarcode in an 

 encysted condition in the form of a compressed ovoid or spheroid ball, of 

 variable size, as seen in figs. 27-29. These specimens also often exhibit a 

 number of pale granular spheres, of variable size, occupying the neck of 



