SIMPLEST FOKMS OF GENERATIVE PROCESS. 439 



frond of the Cryptogamia, and of which the function is only temporary, 

 It is by this organ, the single or double cotyledon, that the nourishment 

 provided in the ovule is absorbed and prepared for the development of 

 the young Plant ; the permanent fabric of which, even at the time of 

 the maturity of the seed, forms but a small proportion of the entire 

 embryonic structure. In the act of germination, however, the perma- 

 nent portions are developed at the expense of the temporary, the plu- 

 mula and radicle absorbing the nourishment which has been elaborated 

 by the cotyledons ; and having fulfilled its transient purpose, and com- 

 pleted its term of life, the first leaf-like expansion withers and dies. 

 The tissues of the young Plant are at first of the simplest possible 

 character ; but as the organs characteristic of its adult condition are 

 one after another put forth (always originating in peculiar groups of 

 cells), so do we find that the spiral vessels, woody fibre, &c., charac- 

 teristic of the higher organisms, gradually make their appearance. Thus 

 we see that even the highest Plants have to pass through conditions 

 closely conformable to those which are permanently shown in the lower ; 

 and that the parts which are first formed are destined for only a tem- 

 porary purpose, that of preparing nourishment for the evolution of more 

 permanent structures. We shall find, in tracing the history of the de- 

 velopment of the higher Animals, that exactly the same general fact 

 may be observed, in even a more striking manner ; the number of diffe- 

 rent stages being greater, and a yet larger proportion of the parts first 

 formed having a merely temporary purpose, and being destined to an 

 early decay, as soon as the more permanent parts of the fabric shall 

 have been evolved. 



782. Among many of the lower Animals, a multiplication of indivi- 

 duals takes place by a process that closely resembles the budding of 

 Plants ; this also must be regarded, not as a proper act of Generation, 

 but as a modification of the ordinary Nutritive process. The same may 

 be said of the powers of reparation, which every Animal body possesses 

 in a greater or less degree, but which are by far the most remarkable 

 among the lower tribes ; for when an entire member is renewed (as in 

 the Star-fish), or even the whole body is regenerated from a small frag- 

 ment (which is the case in many Polypes), it is by a process exactly 

 analogous to that which is concerned in the reparation of the simplest 

 wound in our own bodies, and which, as already explained ( 636), is 

 but a modification of the process that is constantly renewing, more or 

 less rapidly, every portion of their fabric. Although the buds thus 

 produced and separated are usually developed into the likeness of the 

 parent stock, yet this is sometimes not the case, the stock possessing one 

 form, and the bud another, which may be quite different ; as when certain 

 fixed composite Zoophytes bud off free-moving solitary Medusae, these 

 last depositing ova, from which the Zoophytic type is regenerated. 

 When, however, this phenomenon, to which the name of " alterations 

 of generations" has been given (erroneously, in the Author's opinion),* 

 is carefully examined, it is found that the bud thus detached is really 



* For a discussion of this subject, see the Author's "Principles of General and Com- 

 parative Physiology," chap, xviii., sect. 1. 



