Synonyms: See Brady '84 for a long list. "It is impossible to define by any precise characters the morphological range of the present species. Its variations are infinite." (Brady, p. 660.) This very common form, which occurs in all latitudes, was found frequently among the algæ at Woods Hole. Its characters are so difficult to define that for the present I shall limit my record to this brief notice. Size of shell 230µ by 270µ. Genus ACTINOPHRYS Ehr. The body is spherical and differentiated into granular endoplasm and vacuolated ectoplasm, but the zones are not definitely separated. There is one central nucleus and usually one contractile vacuole. The pseudopodia have axial filaments that can be traced to the periphery of the nucleus. Fresh and salt water. Actinophrys sol Ehr., variety. Fig. 5. Synonyms: See Schaudinn '95. The diameter is about 50µ; the vacuolated ectoplasm passes gradually into the granular endoplasm. This is the characterization given _A. sol_ by Schaudinn, and it applies perfectly to the freshwater forms. If I am correct, however, in placing an _Actinophrys_-like form found at Woods Hole in this species, the description will have to be somewhat modified. In this form (fig. 5) there is no distinction between ectoplasm and endoplasm, and there is an entire absence of vacuoles. The nucleus is central, and axial filaments were not seen. The single specimen that I found looked much like a Suctorian of the genus _Sphærophrya_, but the absence of a firm cuticle and the presence of food-taking pseudopodia with granule-streaming makes it a very questionable Suctorian, and 1 place it here until further study throws more light upon it. Diameter of body 40µ; length of pseudopodia 120 to 140µ. [Illustration: Fig. 5.--_Actinophrys sol_.] Genus HETEROPHRYS Archer. The body is globular with but slight differentiation into ectoplasm and endoplasm; one nucleus in the latter; contractile vacuoles one or many; pseudopodia on all sides, thin, and with peripheral granule-streaming; surrounded by a globular, rather thick coat of jelly, which is hyaline inside and granular on the periphery. Fresh and salt water. Heterophrys myriapoda Archer. Fig. 6. Synonym: _H. marina_ Hert. & Less. '74.