GENUS ACANTHOCYSTIS— ACANTHOCYSTIS CH^TOPHOEA. 265 



as long as or longer than the spinous rays. Exterior envelope of the body 

 appearing as an atmosphere of exceedingly minute bacterium-like particles, 

 which are sometimes absent. 



Size. — Diameter of the body ranging from 0.048 mm. to 0.1 mm. ; 

 length of the larger furcate spines from 0.02 mm. to 0.06 mm. ; length of 

 the soft or pseudopodal rays about equal to the diameter of the body or 

 longer. 



Locality. — In the same positions as Adinophrys sol and ActinosphcBrium 

 eichhornii, in quiet waters, among various aquatic plants. Observed in the 

 vicinity of Philadelphia and other places in Pennsylvania, in New Jersey, 

 Ehode Island, Colorado, Wyoming Territory, and Nova Scotia. Found 

 in ponds in the Uinta Mountains of Wyoming Territory, at an elevation 

 of 10,000 feet. 



AcaBithocysti«$ chsetophora, as ordinarily observed under moderate 

 powers of the microscope, resembles the common Sun-animalcule, but with 

 the body of a bright-green color, hence its familiar name of the Green 

 Sun-animalcule. Under high powers of the instrument it is seen to possess 

 a more complex structure, as represented in fig 1, pi. XLIII 



The body of Acanthocystis chcetophora is spherical, and is composed 

 of a basis of finely granular protoplasm, with scattered oil molecules, and 

 variable proportions of globular corpuscles, mostly of nearly uniform size. 

 A clearer central spot indicates the presence of a large nucleus, which may 

 be brought into view by the action of reagents. 



The corpuscles mentioned are commonly for the most part, if not 

 entirely, of a bright-green color, and accord with the characters of cliloro- 

 phyl. They are often very numerous, and appear especially to be con- 

 fined to the more superficial portion of the protoplasmic mass of the body. 

 Often mingled Avith them there are variable proportions of clear, colorless 

 corpuscles, of about the same size, and occasionally individuals are to be 

 found, as represented in fig. 4, in which these exist to the entire exclusion 



of green ones. 



Among the green and colorless corpuscles, from time to time, other 

 globular bodies exist, of variable sizes, some of which are distinguishable 

 as food-balls and vacuoles. Distinct contractile vesicles I have never been 

 able to detect. 



