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IV. — Notices of new American Fresh-water Infusoria. 

 By Alfred C. Stokes, M.D. 



{Read 12th January, 1887.) 



Plate V. 



The ponds, marshes, and stagnant pools of the central portion of the 

 eastern United States seem particularly favoured by the Infusoria. 

 Within their shallows, beneath the shadows of their aquatic vegetation, 

 or clinging to submerged leaflets, to floating objects, or to the nameless 

 fragmental debris at the bottom. Infusoria abound in remarkable pro- 

 fusion. The student of these minute but charming forms of animal life 

 has only to ■ sweep his collecting vessel among the water-weeds, or 

 gently scrape the soft ooze, to be amply rewarded, not only by Infusoria 

 whose beauty shall stir his aesthetic nature, but with forms that will fill 

 him with wonder at their variety of structure, movements, and habits. 

 And another source of interest, if not of surprise, is that so great a 

 proportion of the captives are new to science. To find Infusoria in 

 American ponds and shallow pools that have also been found in European 

 fresh waters is not common. There are cosmopolitan forms even in 

 sweet water, but according to my somewhat limited experience, they are 

 not abundant. What the American margins of the sea may reveal to 

 the Microscope I do not know. It has never been my good fortune to 

 be able to examine a drop of the ocean with Infusoria as the objects, and 

 as far as I am aware, that field is here practically unexplored by any 

 one. 



In the neighbourhood of the writer's home in central New Jersey 

 the level surface of the country is only at irregular intervals sufficiently 

 hollowed to retain the water and produce permanent pools that shall 

 resist the summer sun, but these little depressions are abundant; con- 

 sequently marshy places, small lakes, and almost stagnant pools choked 

 with Sphagnum are easily accessible, and wondrously rich in the lower 

 forms of microscopic animal life. Ehizopoda, Infusoria, and aquatic 

 worms abound, to say nothing of diatoms, desmids, and fresh-water algae. 

 It is from this limited but prolific region that the writer has taken the 

 following hitherto undescribed Infusoria among many others. All the 

 genera here referred to were originally discovered and described by 



EXPLANATION OF PLATE V. 



Fig. 1. — Tetraselmis limnetis X IIOO.J 



2. — Petalomonas pleurosigma x 750. 



3. — Chloropeltis monilata X 585. 



4, 5, 6. — Chrysomonas pulchra X 675. 



7, 8, 9, 10. — Zygoselmis mutahilis x 170. 

 11. — Strombidium gyrans X 360. 

 12. — „ ,, front view. 



13. — Mesodinium fimhriatum x 562,- 

 14. — Pyxidium vernale x 450. 

 15. — „ invaginatum x 420. 

 16. — Vaginicola annulata x 245. 

 17. — Lagenophrys labiata x 486. 

 18. — ,, „ with closed lips x 486. 



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