48 MICROSCOPICAL OBJECTS FOUND 



Infusoria, as they are generally designated, — 

 specimens of the three genera, Campylodis- 

 cus, Coscinodiscus, and Actinocyclus having 

 come under my notice. It is anything but certain 

 that these curious and beautiful creatures do 

 not belong to the same group as the Diato- 

 macese, and that they have in reality no claim to 

 the possession of animal life. In so many points 

 they resemble the siliceous frustules of the former, 

 that I cannot believe them to be distinct. Let 

 any one, to satisfy himself of this, examine and 

 compare a few genera in the following order, 

 — Coscinodiscus, Actinocyclus, Actinoptychus, 

 Heliopelta, Podiscus, Systephania, Triceratium, 

 Zygoceros, and Biddulphia. 



In Coscinodiscus, Actinoptychus, and Actino- 

 cyclus we have the elaborately ornamented circu- 

 lar disk. In the three following genera we find 

 various forms of projections arising up from the 

 external rim of these disks. In Heliopelta these 

 are usually sharp points, but in Podiscus they 

 are obtuse protuberances, very like those forming 

 the angles of many Diatomacese. In Tricera- 

 tium we have very similar appearances, only 

 the circle has degenerated into a triangle, with 



