PROTOZOA. EHIZOPODA. 435 



and the simplest Protozoon, in regard alike to the nature of the 

 aliment on which each respectively is supported, and to the means 

 by which that aliment is introduced (§180). Hence these simplest 

 members of the two Kingdoms, which can scarcely be distinguished 

 from each other by any structural characters, seem to be physio- 

 logically separable by the mode in which they perform those actions 

 wherein their life most essentially consists ; for the Protophyte de- 

 composes Carbonic acid under the influence of Light, and generates 

 ChloropLyll and Albuminous compounds, in a manner in all 

 respects comparable to that in which the same operations are 

 performed by the leaf-cells of the most perfect Plant ; whilst the 

 Protozoan ingests and digests both Vegetable and Animal food, and 

 applies it to the nutrition of its body, no less effectively than an 

 Animal possessing the most complex digestive and circulating ap- 

 paratus. And in the present state of our knowledge, we seem justi- 

 fied in laying it down as the most ready and certain differential 

 character we are acquainted with, between those Protophytes and 

 Protozoa which are apparently most closely related to each other 

 in the simplicity of their structure, that the former (with the 

 exception of the Fungi) decompose carbonic acid under the in- 

 fluence of light, and acquire a red or green colour from the new 

 compounds which they form in their interior ; whilst the latter, 

 having no such power, receive animal and vegetable organisms, or 

 pai'ticles of such, into the interior of their bodies, where they 

 extract from them the ready prepared nutriment they are fitted to 

 yield.* 



325. PvHizopoda. — The lowest Order of the Protozoa consists of 

 a group of minute animals which were formerly ranked among 

 Infusoria, but were first separated from that group by Dujardin, 

 who conferred upon them the name by which they are now known ; 

 that name (which means 'root-footed ') being the most appropriate 

 expression yet given of the leading feature in their organization, 

 namely, the extension of their sarcode-body into long processes, 

 termed pseudopodia (false feet), which serve at the same time 

 as instruments of locomotion and as prehensile organs for ob- 

 taining food. The other characters by which this group is 

 distinguished from ordinary Animalcules are for the most part 

 negative ; consisting in the absence of any definite mouth or 

 digestive cavity, and in the want of an enveloping membrane 

 sufficiently firm to resist the introduction of particles from with- 



* Many instances have been cited, of Animalcules acquiring a green 

 colour by the decomposition of Carbonic acid under the influence of 

 light ; but there can be no doubt in the niind of any one who is familiar 

 with the results of recent Microscopic research, that in all these cases 

 the supposed Animalcules were really Protophytes. The peculiarities in 

 the nutrition of Fungi, which have been already adverted-to (§§ 263-270), 

 whilst separating them from ordinary Protophyte3, do not give them any 

 title to a place in the Animal kingdom. 



F P 2 



