INTRODUCTION TO CRYPTOGAMIC BOTANY, 87 



prejudice either way, till a certain number of bodies, ascer- 

 tained to be precisely of the same nature, be isolated, and the 

 changes of these observed, with every possible precaution, to 

 avoid en-or. At present, it seems to me that there is not by 

 any means sufficient proof that the objects in question really 

 arise from germs of the same nature. The second remark I 

 would make is, that there appears, too often in treatises of this 

 description, to be great indistinctness as to the notion of what 

 a species really is. We know that in the course of development, 

 higher bodies go through a yast variety of phases, which resem- 

 ble closely true substantial species which have arrived at their 

 full development, but we are not therefore to suppose that in 

 passing through these phases the production has really con- 

 sisted of such a number of real species. In the Agardhian 

 sense this may be true enough, for when he pronounces the 

 vessels and cells of phtenogamous plants to be Algge, his rea- 

 soning apjDcars to be, however strongly he expresses himself, 

 merely that they are representatives of Algge, and resemble 

 them in structure. I would remark, also, that the real difficulty 

 of the case does not depend on the question as to the difference 

 of animal and vegetable life. These evidently in certain parts 

 of the creation are so intimately combined, that it is quite im- 

 possible to say where the one ceases, and the other begins ; and 

 there is really no reason why we should be incredulous as to the 

 jjossibility of the same object being at one time endowed more 

 especially with animal, and at another with vegetable life. 

 Late observations on the reproductive bodies of some Alga3 

 show that their motion is produced by vibratile cilia, exactly 

 in the same way as in certain animals. But it is exceedingly 

 difficult to imagine the transformation of one real species into 

 another. The same species may assume a vast variety of forms, 

 according to varying circumstances, and it is highly instructive 

 to observe these changes ; but that the same spore should, 

 under different circumstances, be capable of producing beings 

 of an almost entirely different nature, each capable of repro- 

 ducing its species, is a matter which ought not to be admitted 

 generally without the strictest proof Observations made with 

 care on isolated individuals, and not on a common mass, which 



