PLATE XXVII. 



AECELLA VULGARIS. 



In most of the figures of Arcella in this and the succeeding plates the cancellated or dotted appear- 

 ance of the shell is omitted. The color is less varied than in the originals. 



Figs. 1, 2. Lateral and inferior views of the same individual, with extended pseudopods. Bog on 

 the Schuyltill, West Philadelphia, June, 1877. 250 +. 



Fig. 3. Lateral view of an empty shell. Ditch below Philadelphia. 250 -f-. 



Fig. 4. Lateral view of a colorless, transparent individual, with projected pseudopods, and Bar- 

 code attached to the interior of the shell by tapering threads. Swarthmore brick-pond, Delaware 

 County, Pa., September, 1874. 500 +. 



Fig. 5. Individual with colored shell, the sarcode visible within. Same locality, and magnified 

 same degree. 



Fig. 6. SheU. of a small individual. Original was living, and the shell of a brown color. Fort 

 Bridger, Wyoming Territory, August, 1877. 250 -(-. 



Fig. 7. Lateral view of an active individual, with sarcode visible, with protruded pseudopods, 

 and with pale yellow shell. Absecom pond. If. J., April, 1876. 350 +. 



Fig. 8. Upper view of a colorless individual. The sarcode attached by tapering threads to the 

 interior of the shell ; around its border five contractile vesicles visible, and more internally a pair of 

 nuclei opposite each other. The dotted appearance of the shell represents the cancellated structure. 

 a, one of the nuclei. Fairmount Park, Philadelphia, June, 1878. 250 +. 



Figs. 9, 10. Two views of the shell from a living specimen ; inferior view ehowing a crenulated 

 mouth, and lateral view showing the inflection of the base to the mouth. Absecom pond, Kew Jersey, 

 August, 1876. 350 +. 



Figs. 11, 12. Lateral and upper views of au individual, with the sarcode visible, and with pro- 

 jected pseudopods. a, nuclei; h, contractile vesicle; c, amoeboid corijuscles in the interval between 

 the sarcode and the shell ; d, large air-bubble. Fairmount Park, June, 1877. 250 -)-. 



Fig. 13. Inferiorviewof a similar specimen. Ditch below Philadelphia, September, 1877. 250 -|-. 



Figs. 14, 15. Inferior and lateral views of the same individual. In the former view the sarcode 

 appears of irregular form, and it exhibits a single nucleus and three contractile vesicles. Absecom 

 pond. New Jersey, June, 1877. 250 -|-. 



• Fig. 16. Small shell (of a dark ochreoue color) with pitted surface. Woodstown pond. New Jer- 

 sej', September, 1877. 250 -|-. 



Fig. 17. Side view of a pair of individuals in conjugation, both of the same size ; the shell of one 

 diirker than the other. Sw.arthmore brick-pond, September, 1874. 250 -f. 



Fig. 18. Inferior view of a specimen, living and active, in which portions of the shell appear as 

 if bitten out. Atco,N. J., June, 1877. 250 -1-. 



Figs. 19, 20. Inferior and lateral views of ait individual, with constricted shell. Fairmount Park, 

 Philadelphia, May, 1878. 250 +. 



Figs. 21, 22. Upper \iews of two minute specimeus, probably young individuals, with the sarcode 

 showing a single nucleus and several large contractile vesicles. Atco, N. J., October, 1877. 1,000 +. 



Fig. 23. Lateral view of a living specimen, with pitted shell. China Lake, Uinta Mountains, 

 Wyoming Territory, August, 1877. 500 -f. 



Fig. 24. Two similar individuals in conjugation, with the shells of different shades of color. With 

 the preceding. 



Figs. 25, 26. Inferior anji lateral views of an individual, with pitted shell. Swarthmore, Delaware 

 County, Pa., April, 1874. 350 +. 



!Figs. 27, 28: Superior and laterul views of an empty shell, with irregulaily pitted surface. Same 

 locality. 



Figs. 29, 30. Lateral aud inferior views of an individual, with pitted shell. Ditch below Phila- 

 delphia, June, 1876. 350 -|-. 



Fig. 31. Lateral view of a^specimen. Fort Bridgpr, Wyoming Territory, August, 1877. 250 +. 



Figs. 32, 33. Lateral aud inferior views of a specimen, with the sarcode encysted, and surrounded 

 with flocculent matter, probably excrembutitious. Atco, N. J. , June, 1877. 5t0 -|-. 



Fig. 34. Upper view of an empty colorless shell. Smarthmore brick-pond, September, 1874. 350 + 



Fig. 35. Cancellated structure of the shell of Arcella highly magnified. 



