156 THE RELATIONS OF PHYTOZOA 



ingly concluded that Volvox and Gonium are animals, simply 

 on the grounds of their having this contractile vesicle. 



There is one feature, however, which would yet seem to mili- 

 tate against their being animals, and that is, they have never 

 been seen to take in food ; but as a set-off to this, there are 

 beings of an undoubted animal nature which do not take in 

 food into a stomach. Some of the intestinal worms, Tsenia, 

 have no stomach, but absorb their fluid nourishment through the 

 porous skin of the body ; and therefore we are allowed to sup- 

 pose that Volvox may possibly do the same. 



So you see that although the Volvox, Gonium, and I will 

 add many other related kinds of animalcules, have one or two 

 strong animal characteristics, the most positive of which is the 

 contractile vesicle, yet, on the other hand, their vegetable char- 

 acteristics, especially in the mode of reproduction, are just as 

 strongly in favor of the botanist's claim to them. On account 

 of these mutually common characteristics, the lowest forms 

 have been called, by some naturalists, Phytozoa, i. e., plant- 

 animals. 



Commencing now with these " Plant-animals," let us see 

 where they will lead us if we follow them through their suc- 

 cessively rising grades of complication. As I have already made 

 you acquainted with the characters of all those which I shall 

 mention in this series, I need only to call them to mind in the 

 same succession as that in which I formerly described them, in 

 order that you may trace their progress from the lower to the 

 higher types. First among them comes the doubtful Volvox, (p. 

 153, fig. 92,) then the more decidedly animal organization of 

 Euglena, (p. 144, fig. 86,) and then Chlamidomonas, (p. 145, fig. 

 87,) Heteromastix, (p. 146, fig. 88,) Ceratium, (p. 148, fig. 89,) 

 Pleuronema, (p. 148, fig. 90,) &c., &c., until, if we go on, the 

 highest of the Protozoa crown the series. Or I might commence 

 with another of the doubtful plant -animals, the Sponge, (p. 

 41, fig. 21,) and through the Actinophrys, (p. 44, fig. 22,) pass 

 to Lithocampe, (p. 49, fig. 23,) Zooteira, (p. 50, fig. 24,) 



