94 GENERAL HISTORY OF THE INFUSORIA. 



on this, as has been clone with those on the other side of the question . 

 Meneghini enters the lists with Kiitzing, and disputes the conclusions arrived 

 at by him, rather than the facts on which they rest. 



The first argument, founded on external resemblance, has little value, and 

 offers no certain indications of affinities. However, taking Kiitzing' s state- 

 ments in his own words, modem research has added to its weight ; for it 

 has proved, what was before only a probability, that the so-called Monad- 

 masses are only of a vegetable nature. 



The second reason advanced has been already discussed, whilst the thii'd 

 rests as yet on incomplete observations, and in Meneghini' s opinion has an 

 equally strong analogy in animals, for example, " in the ovaries of PoIj^dcs 

 and other inferior animals, as in many 0\ipara of superior classes. And, in 

 fact, the bag of a spider, with the thousands of small eggs that it contains, 

 seems to me quite as like, as the spore of an Alga, to the organ of propaga- 

 tion of a Scliizonema or a Micromccja.''^ These analogies cannot be allowed 

 much weight, whilst it is, on the contrary, pretty clearly ascertained that the 

 sporangia of Diatomeae produce a brood of young forms within them, — a 

 phenomenon according in all particulars with the mode of reproduction in 

 numerous Algae and Fungi. 



The foui^th argument for their vegetable nature must be admitted to possess 

 great importance. Since Kiitzing enunciated it, the apparent objections 

 against the vital phenomena in question being restricted to plants, have been 

 removed by subsequent inquiry. The green Monads and Euglence, cited by 

 Kiitzing, are now recognized to be vegetable, and can no longer east doubt, by 

 reason of an assumed animal nature, on the fact of the evolution of oxygen 

 being a characteristic of vegetable life. The evolution of oxygen, as Prof. 

 Smith, like every other careful observer, tells us, " may be noticed in any 

 mass of Diatomacea3 during the warmer months of the year, or in gatherings 

 freely exposed to the sun, in the elevated temperature of a confined apartment, 

 during the winter or spring. Under these conditions the water in the vessel 

 becomes covered with mmute bubbles of oxygen, and portions of the Diato- 

 maceous stratum are floated up by the buoyancy of the globules of this gas 

 adhering to their frustules. Such phenomena can only be accounted for by 

 supposing that the Diatomaceae are plants, and that they exhale, like all 

 plants in a state of active vegetation, oxygen from their tissues ; but this pro- 

 cess is iiTeconcilablc with the hypothesis of their animal nature." (Si/noj)s. 

 vol. ii. p. XX.) 



Prof. Carpenter insists {Microscope, p. 469), that the most positive and 

 easily defined distinction between Protophyta and Protozoa "lies in the 

 nature of the aliment, and in the method of its introduction," in each case. 

 " For whilst the Protophyte obtains the materials of its nutrition from the 

 air and moisture that surround it, and possesses the power of detaching 

 oxj'gen, hydrogen, carbon, and nitrogen from their previous binary combina- 

 tions, and of uniting them into ternary and quaternary organic compounds 

 (chlorophyll, starch, albumen, <S: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 pre- 

 viously elaborated by other beings. But further, the Protophyte obtains its 

 nutriment by mere absorption of liquid and gaseous molecules, which pene- 

 trate 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 the 

 simplest members of the two kingdoms, which can scarcely be distinguished 



