268 FEESH-WATEE RHIZOPODS OF NOETH AMEEIOA. 



of Acanthocystis pallida. Mr. Archer* regards it as an accidental colorless 

 form of Acanthocystis turfacea Probably it is one of the stages of life 

 through which the ordinarj^ green-colored animal may have to pass. 



In one instance I observed a colorless individual of A. ch<stophora, 

 0.048 mm. in diameter, which contained, besides numerous colorless cor- 

 puscles, a single bright-green ball. The animal was in active condition, 

 and, while slowly gliding by, it lifted a portion of its armor, and discharged 

 the green ball. 



An individual of pecuhar character, perhaps related with Acanthocystis 

 chBtophora as to form a stage in its history, is represented by fig. 5, pi. 

 XLIII. It was obtained from Absecom pond. New Jersey, September, 

 1874, and was the only one of the kind observed. The body was elon- 

 gated ovoid and transparent, and was filled with large, clear, irregularly 

 polyhedral vesicles, together with a few small green corpuscles. The sur- 

 face and rays were of the same character as in the ordinary condition of 

 A. chcetophora, and a granular layer likewise invested the body. 



Occasionally I have found an empty sac of clear homogeneous mem- 

 brane, and fragments of others, with attached furcate spines like those of 

 A. chcetophora. Fig. 6 represents a specimen of the kind, within which was 

 an oval egg-like body with brownish granular contents and a few scattered 

 green corpuscles. The empty membranes I have suspected to be the 

 exterior covering of A. chcetophora, left by the animal or its progeny of 

 germs after passing through the encysted condition. 



ACANTHOCYSTIS ? 



Plate XLIII, figs. 7-13. 



Body spherical, usually bright green from the presence of abundance 

 of chlorophyl corpuscles ; sometimes colorless from the absence of the lat- 

 ter; or of other colors. Spinous rays numerous, exceedingly delicate, 

 emanating from minute lenticular disks at the surface of the body, and 

 simply pointed at the distal end Enveloping layer of protoplasm finely 

 granular; sometimes absent. Pseudopodal rays longer than the former. 



Sise.— From 0.036 mm. to 0.048 mm. in diameter. 



Locality. — Among aquatic plants in ponds and ditches. Pennsylvania, 

 New Jersey, Wyoming Territory. 



* Quarterly Journal Microscopical Science, 1876, 362. 



