14 Marvels of Pond- Life. 



assumption founded merely upon the negative evidence 

 of their not having been discovered, and the complete 

 absence of " vessels '' cannot be affirmed. 



In the last edition of ^Pritchard's Infusoria/ to which 

 some of our ablest naturalists have contributed, after 

 separating two groups,, the Desmids, and the Diatoms, 

 as belonging to the vegetable world, the remainder of 

 the original family of infusoria are classified as Phytozoa, 

 Protozoa, Rotifer a, and Tardigrada. We shall explain 

 these hard names immediately, first remarking that the 

 Desmids and the Diatoms, concerning whom we do not 

 intend to speak in these pages, are the names of two 

 groups, one distinctly vegetable, while the other, 

 although now generally considered so, were formerly 

 held by many authorities to be in reality animal. The 

 Desmids occur very commonly in fresh water. We have 

 some among our Confervse. They are most brilliant 

 green, and often take forms of a more angular and 

 crystalline character than are exhibited by higher 

 plants. The Diatoms are still more common, and we 

 see before us in our water-drop some of their simplest 

 representatives in the form of minute boats made of 

 silica (flint) and moved by means still in dispute. 



Leaving out the Desmids and Diatoms, we have said 

 that in Pritchard^s arrangement the views of those 

 writers are adopted who divide the rest of the infusoria 

 into four groups, distinguished with foreign long-tailed 

 names, which we will translate and expound. First 

 come the Phytozoa, under which we recognise our old 

 acquaintance zoophyte turned upside down. Zoophytes 

 mean animal-plants, Phytozoa mean plant-animals. We 



