456 Dr. L. Radlkofer on Fecundation in the Vegetable Kingdom, 



However, the spore-cell, which enlarges and becomes tubular, 

 still remaining simple, before propagation, cannot be considered 

 equivalent to even a very young Alga-thread, and in so far, there- 

 fore, the gcrm-cclls (zoospores) asexually produced from it cer- 

 tainly ascend to a higher stage of metamorphosis, since they do 

 not become resting-spores again, but perfect Algse. 



That the form of the alternation of generations is here the 

 same, or nearly the same, as in the asexual multiplication of the 

 developed plant, is certainly a peculiar, yet in our eyes irrelevant 

 condition. AVhen Cohn* sees a resemblance, in the case above 

 mentioned, to the origin of several embryos in the ova of Pla- 

 naria, the well-founded doubt which may be entertained of the 

 correctness of the observation of the latter point is sufficient to 

 make me v, ithhold my assent ; besides that I can by no means 

 compare the swarming-spores to an embryo. On the other 

 hand, I believe I have better right to introduce here another 

 case from the Animal Kingdom, as analogous to ours, in which 

 likewise a very early asexual multiplication occurs combined with 

 an immediately advancing metamorphosis, — the case, namely, 

 of Alcyonella, whose rudimentary embryo (nurse) gives birth by 

 a kind of gemmation to tico tufts of polypes f. 



In regard to the W^ds. fecundated by conjugation, I have nothing 

 to add to what I have already said, or to what is indicated in the 

 Tables. Here, also, the perfect spore presents itself as a nurse ; 

 as in Palmogla'a, and probably also in the conjugation-bodies of 

 Mesocarpus and Staurucarpus, referred to in a former page. 



In conclusion, I subjoin a third Table, in which on the one 

 hand the spore, on the other the embryo contained in the seed, 

 are taken as the point of departure of the individual cycle of 

 development, and the separate stages of development placed to- 

 gether in the order of time. The contradictions which occur 

 from this view are too striking for it to be requisite to point 

 them out in detail, and this comparison can only serve to set in 

 a still clearer light the validity of the developments which have 

 been stated in this essay. 



[Note. — To the Fucoideje (J. Ag.) furnished with antheridia, mentioned 

 at page 258, should be added, from Thuret's observations, Tilopteris Mer- 

 tensii. Kg. (Ectocarpus Mertensii, Ag.) and Dictyota. The antheridia 

 and spermatozoids of the latter genus resemble those of the Florideae {vide 

 Thuret, Ann. des Sc. nat. 4 ser. iii. 1855). 



To p. '2bd. — An enumeration of the Florideae in which the existence of 

 antheridia has been demonstrated is given in the same memoir of Thuret. 

 Al. Braim has also discovered antheridia in Bafrackospermum, which Thuret 

 includes among the FloridcEe (Algar. Unicellul. genera nova, &c. Leipsic, 

 1855, p. 105).] 



* Entw. u. Fortpflanz. der Sphceroplea, p. Ifi (Annals, ser. 2. xviii. p. 81 ). 

 t See Siebold, Vergleich. Anatomie (1840), p. 33. 



