PLATE XLIII. 



Figs. 1-6.— ACANTHOCYSTIS CHJLTOPHORA. 



Fig. 1. A green individual. Common form, in the vicinity of Philadelphia, among various 

 aquatic plants. Ditches below Philadelphia!, September, 1874. 750 diameters. 



Fig. 2. One of the longer furcate spines more highly magnified. 



Fig. 3. One of the smaller furcate spines more highly magnified. 



Fig. 4. A colorless individual. Less common than the former variety. Swarthmore brick-pond, 

 Delaware County, Pennsylvania, May, 1*74. 1,000 diameters. 



Fig. 5. An elliptical form, supposed to pertain to the same. Absecom pond, New Jersey, Septem- 

 ber, 1874. i7."> diameters. 



FlG. G. Supposed Bhed capsule, containing a few green grains aud a brownish ovum-like body. 

 Fort Bridger, Wyoming Territory, July, 1877. 250 diameters. The capsule was crowded with long aud 

 short furcate spines like those of the figure. 



Figs. 7-12.— AC ANTHOCYSTIS ? With simple spines. 



Fig. 7. Bright green individual. Fort Bridger, Wyoming Territory, August, 1877. 750 diameters. 



Fig. 8. Green individual. Fort Bridger, July, 1877. 500 diameters. 



Fig. 9. A bright red individual. Spring on Darby Creek, Delaware County, April, 1875. 700 

 diameters. 



Fig. 10. A colorless individual. Atco, N. J., October, 1877. 656 diameters. 



Fig. 11. Colorless individual. Broad Mountain, Pennsylvania, September, 1876. 500 diameters. 



Fig. 12. Colorless individual, with the protoplasmic mass iu an encysted condition, enclosed in a 

 spinous capsule. With Ceratophyllum, from Bristol Canal, Pennsylvania, December, 1877. 638 

 diameters. 



Fig. 13. Fragment of membrane, supposed to be a portion of a moulted capsule of Acanthocystis. 

 Fort Bridger, Wyoming, August, 1877. 500 diameters. 



Figs. 14-16.— ACANTHOCYSTIS ? With short pin-like spines. 



Fig. 14. Individual, with the interior occupied by a mass of protoplasm containing a nucleus and 

 a vacuole, but emit ting no pseudopodal rays. 



Fig. 15. An individual with the protoplasm contracted into a ball, floating in a thinner liquor, 

 and exhibiting at the periphery three vacuoles. 



FlG. 1G. An individual with the interior protoplasmic mass apparently ready to assume the 

 eucystcd state. All three specimens collected with others in a pond in Fairmount Park, West Philadel- 

 phia, August, 1878. 666 diameters. 



