PRIXCHARD's history of infusoria. 1 23 



The vegetable Infusoria include the Diatoms, the Desniids, and cer- 

 tain other organisms which most botanists regard as low forms of Algae. 

 All these Infusoria are sometimes spoken of collectively as constituting 

 a single group, termed Protophyta. 



But what are Protophyta? The word itself seems suggestive of 

 a vegetable group, holding a position among plants akin to that which 

 Protozoa occupy in the animal kingdom. Such an answer must, how- 

 ever, be regarded as inconsistent; for no botanist has yet proposed to 

 elevate the Protophyta to the rank of a sub-kingdom, while the Protozoa 

 form one of the five primary departments of the animal world. True 

 it is that botanists are slow to acknowledge the systematic value of 

 the several groups which constitute the great division of Cryptogams; and 

 it may even be questioned whether these last do not bear to Phaeno- 

 gams a relation somewhat similar to that between Invertebrate and 

 Vertebrate animals. This, at least, must be admitted, that the Cryp- 

 togams differ much more inter se than do the Phaenogams ; and it is 

 difficult to mention any positive anatomical feature common to all the 

 members of the former sub-kingdom. Their reproductive organs are 

 often not homologous. And, assuredly, the " spore" of a Moss by no 

 means corresponds with what is called the spore of a Fern. With 

 regard to the Protophyta in particular, all that can be said is, that they 

 constitute a sub-group of the large class of Algae ; but whether equiva- 

 lent to the Chlorospermeae, or to all the thalloid Algae taken together, 

 it is, at present, not easy to determine. To define the Protozoa as 

 unicellular animals, and the Protophyta as unicellular plants, not 

 merely requires the assumption of a theory which is, at best, very far 

 from proven, but contradicts directly the plain testimony of observed 

 facts, both in the structure and development of these highly diversified 

 forms. 



As to the animal Infusoria, they consist of — 



1. Rhizopoda, 



2. Infusoria proper, 



3. Doubtful embryonic forms, and 



4. Eotifera. 



The Eotifera now form part of the Annulose sub-kingdom. The 

 Rhizopoda and Infusoria have been placed by Siebold in the sub-king- 

 dom Protozoa. 



A copy of the " Infusionsthierchen" lies before us, while we pen 

 the present page. It forms a huge folio volume of 550 pages, with an 

 atlas of sixty- four coloured plates. The characters of the several groups 

 are in three different languages, Latin, German, and French. It is 

 impossible to consult this (in every sense) great work, without some 

 feeling of admiration for the prodigious industry which, in the year 

 1838, and with inferior instruments, could accumulate so many hun- 

 dred figures and descriptions of living beings, all of minute size, and 

 many for the first time made known to science by their distinguished 

 investigator. 



