236 FRESH- WATER EHIZOPODS OF NORTH AMERICA. 



The body of Actinophrys sol is soft and elastic, and though ordinarily 

 spherical, occasionally, by feeble contraction, exhibits a slight change from 

 the regular outline of form. Its surface is not even, but wavy or botryoidal, 

 though sometimes this appearance is hardly evident. The body is composed 

 of a basis of colorless, hyaline protoplasm with diffused, pale, granular matter 

 and fine oil-like molecules. The protoplasm is crowded with clear globules 

 or vacuoles, of comparatively uniform size, which give the body the appear- 

 ance of being a foamy mass. Often these globules are so numerous, that 

 the body of the Actinophrys appears to be made up of them, with barely 

 sufficient protoplasm to hold them together and give to the whole a thin 

 investment. When crowded, they become more or less polyhedral; and 

 those at the periphery project slightly beyond the general outline, so as to 

 give it the botryoidal appearance. Though usually of comparatively 

 uniform size, they may vary considerably in different individuals and 

 occasionally in the same individual. See figs. 1—5, 7—10. 



Rarely have I seen what I have taken to be an individual of Artino- 

 phrys sol in which vacuoles, excepting the contractile vesicle, were altogether 

 absent, as represented in fig. 6. 



A large nucleus occupies a central position of the body, but is rarely 

 even indistinctly visible, until brought into view by artificial means, — the 

 action of acetic acid or other chemical reagent. When seen, it appears as a 

 pale, faintly granular ball containing a darker nucleolus. 



On one occasion I observed an individual, as represented in fig. 5, in 

 which a nucleus was very distinctly visible. The animal appeared to be 

 undergoing dissolution, and the figure represents it as first seen. The body 

 consisted of a mass of granular protoplasm, with a single layer of large 

 vacuoles occupying the periphery, and from it there projected only five 

 pseudopodal rays. The animal was stationary and its vacuoles quiescent, 

 but after a time several of these slowly expanded and became more 

 prominent, then successively collapsed, and after an hour all had disap- 

 peared, leaving the body in a shriveled condition. The nucleus remained 

 persistent, and was more distinct at last than at first. It was globular, and 

 contained many granules of uniform size and a large central nucleolus. 



Commonly, at some portion of the periphery of the body of Actinophrys 

 sol, there appears a contractile vesicle. At one moment it may be undistin- 

 guishable from the contiguous vacuoles, but becomes evident from its 



