128 GEXEEAL HISTOEY OF THE I^FUSOEIA. 



produced with such rapidity as would lead to the conclusion that the germs 

 from which they originate must have pre-existed in the cells in which they 

 appear (as in the Characece), without interfering Avith their functions. " Young 

 Astasice are also developed within the cells of Sjpirogyra to a great extent ; 

 and although they at first have almost as much polymorj^hism as an Amoeba, 

 still they retain their cihum, and after awhile assume the form and move- 

 ments peculiar to Astasia. On one occasion I saw a large Amoeba with a 

 long cilium at one time assuming the form of an Astasia, and at another 

 that of an A7noeba, which thus gives the link between these two Infusoria. 

 The cihum, however, had not the power of the filament of Astasia, though it 

 occasionally became terminal." 



Developments of a similar Ehizopodous character are, he goes on to say, 

 frequent in Eurjlena : — " I was led to notice this development by an apparent 

 metamorphosis of the cell- contents of some fixed and capsuled EacjJence into 

 granuliferous Amoebce, of a pinldsh colom% within the old cell of Euylena 

 itself ; and the presence of several such Amoebce creeping about the watch- 

 glass, while many of the cells of the EwjJence (viridis'?) were empty, or only 

 contained a little effete matter, left no doubt in my mind as to the origin of 

 both coloiu' and infusorium. It was also observed in some instances, where 

 the contents of the Euglena had passed into an Amoebous mass, that the 

 latter imderwent a kind of segmentation, so that several (perhaps eight) 

 small Amoebce were developed instead of one large one." 



Of the nature of Phttozoa. Animal and Vegetable Chaeactees. — 

 The collection of organisms we have grouped together for convenience' sake, 

 and from want of a better arrangement, under the name of Phytozoa, is 

 actually so heterogeneous that no general discussion respecting the natm-e of 

 them as a class is practicable, whilst, at the same time, a separation between 

 vegetable and animal forms is equally impracticable. The remarkable phases 

 of existence through which any one species may pass upsets all our notions 

 based on presumed constant characters : for, as we have seen, one and the 

 same being may at one period of its existence exhibit in a preponderating 

 degree the vital phenomena of an animal, at another those of a plant, 

 whence has arisen the h5T^)othesis of the metamoq^hosis of plants into 

 animals, and vice versa, — an idea that has foimd little favoui% being opposed 

 to the prevaihng belief of the fixity of nature imposed on all beings. The 

 real fact of the case is, that we have no certain criterion between the two divi- 

 sions of organic natiu^e which can be relied on and practically resorted to in 

 cases of difiiculty, such as many of the Phytozoa present. 



Some natiu'alists have broached the notion that the phases of existence of 

 a presumed animal or plant, which resemble in outward aspect supposed 

 independent species or genera, are not identical with them ; so that, for 

 instance, the animal-looking Amoeba Hartig met with in the developmental 

 series of Phytozoa of antheridia should not be considered really an animal 

 Amoeha, but merely a vegetable mass simulating one. So, again, in Proto- 

 coccv.s they would deny anything but external gene^-al characters to exist in 

 common between its forms of development and the several genera Cohn would 

 assimilate them with. There may be some truth in this supposition — there 

 may be real animal organisms and true vegetable coinciding in form, yet 

 distinct in natiu'e ; but the onus lyrobancU rests with those who will make 

 this distinction. 



However this may be, the advance of science has rendered it certain that 

 some families and genera which Ehrenberg, and most obseiwers before his era, 

 reckoned among animals, are rightly to be numbered among plants, whilst 

 of others, again, it must still be said their position is doubtful. Deferring 



