COMPARISON OP PROTOZOA AND PROTOPHYTA. 409 



originated. As the condition of an Actinophrys undergoing 

 selt-division is to all appearance the same as that of two indivi- 

 duals in incipient conjugation (Fig. 192, b), it cannot be deter- 

 mined in any particular case which operation is in progress, 

 until the creature has been watched sufficiently long for the ten- 

 dency of its changes to become apparent. 



263. If, now, we compare the foregoing history with that of 

 Palmoglcea or any other simple Protophyte, we shall see that 

 whilst there is a strong analogy between the two sets of pheno- 

 mena, there are at the same time certain most important dif- 

 ferences. One of the most obvious of these differences, lies in 

 the movements exhibited by the Amceba and Actinophrys ; for 

 although these are by no means sufficient in themselves (as was 

 once supposed) to establish the distinction between the Animal 

 and Vegetable kingdoms, yet, when they do not consist in the 

 mere vibrations of cilia, such as are executed by zoospores, an- 

 therozoids, &c., among Plants, but depend upon alterations in a 

 contractile substance forming the entire body, they bear a much 

 closer resemblance to the actions of higher Animals ; and we 

 may trace in fact, in the ascending animal scale, a progressive 

 specialization or setting apart of certain portions of the contrac- 

 tile substance more peculiarly endowed with this property, until 

 they take the form of distinct muscular bands. A more positive 

 and easily defined distinction lies in the nature of the aliment of 

 the Protophyta and Protozoa respectively, and in the method of 

 its introduction. For whilst the Protophyte obtains the materials 

 of its nutrition from the air and moisture that surround it, and 

 possesses the power of detaching oxygen, hydrogen, carbon, and 

 nitrogen, from their previous binary combinations, and of uniting 

 them into ternary, and quaternary organic compounds (chloro- 

 phyll, starch, albumen, &c.), the simplest Protozoon, in common 

 with the highest members of the Animal kingdom, seems utterly 

 destitute of any such power, and is dependent for its support 

 upon organic substances previously elaborated by other beings. 

 But further, the Protophyte obtains its nutriment by mere ab- 

 sorption of liquid and gaseous molecules, which penetrate by 

 simple imbibition ; whilst the Protozoon, though destitute of any 

 proper stomach, makes (so to speak) a stomach for itself in the 

 substance of its body, into which it ingests the solid particles 

 that constitute its food, and within which it subjects them to a 

 regular process of digestion. Hence these simplest members of 

 the two kingdoms, which can scarcely be distinguished from each 

 other by any structural characters, seem to be physiologically sepa- 

 rable by the mode in which they perform those actions wherein 

 their life most essentially consists ; for the Protococcus-cell de- 

 composes carbonic acid under the influence of light, and gene- 

 rates chlorophyll and proteine compounds, in a manner in all 

 respects comparable to that in which the same operation is per- 

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



