442 Dr. L. Kadlkofer on Fecundation in the Vegetable Kingdom, 



dated ova*. In the second place, it seems to me a settled 

 fact, that the part played by the spermatozoid ^fter penetration 

 into the ovum in fecundation, whether it be a ferment or any- 

 thing else, is not connected with its shape, but purely with the 

 substance of which it is composed, and consequently that w^e 

 need not particularly wonder, if we should meet anywhere in 

 nature with a fecundating substance — I might say spermatozoids 

 ■ — without definite, independent form. 



From each vitellus is produced first of all an individual being 

 {the embryonal vitellus itself appears to a certain extent as 

 suchf). It either remains as such until at the highest stage of 

 its development it has acquired the power of sexual reproduction, 

 or it becomes multiplied before that epoch by asexual propagation 

 (by formation of gonidia and buds, division). A special form of 

 this asexual propagation, in which the progeny, either of the first 

 or of a subsequent generation, appear from their origin onward % 

 under a form unlike that of the asexual plant — as nurses — is 

 known by the name of alternation of generations^. This is a 



* Leuckart, Article * Zeugung/ in Wagner's Handworterbueh der Phy- 

 siol. Bd. iv. p. 958 (1853). I shall not refer here to the observations of 

 development of individuals from unfecundated ova of Daphnia, Talceporiay 

 Psyche, &c., the explanation of which is perhaps still to be discovered. 

 But, as will be seen clearly in the sequel, the clothing of the unfecundated 

 spore of Fucus by a cellulose membrane, and the formation of tubular pro- 

 longations from these, is certainly connected with the above questions. 

 (Thuret, Ann. des Sc. nat. 4 ser. ii. p. 204, 1854.) 



t I consider myself quite justified in leaving unnoticed, as insufficiently 

 estabUshed, the single case, as yet contradictory of the above, of the occur- 

 rence of several embryos in one ovum in Planaria. The accounts given 

 by Van Beneden of a subdivision of originally sim])le ova of Tubularia and 

 Hydractinia into several smaller ova, each of which produces an embryo, 

 are, as Prof. Gegenbaur of Jena informs me, already refuted ; and also those 

 of Koren and Danielssen, forming a counterpart to the former, as to a sup- 

 posed fusion of every 20-40 of the fecundated ova of the Gasteropodous 

 genera Buccinum and Purpura into a common mass, which produced only 

 one single embryo. [See on this point Ann. Nat. Hist. ser. 2. xix. pp. 336, 

 433, and xx. p. 6. — A. IL] 



X Following Leuckart, we do not include in the conception of alterna- 

 tion of generations the case ceijtainly not yet discovered in the Animal 

 Kingdom, but conceivable, and actually occurring in the Vegetable King- 

 dom — in the propagation of Algae by zoospores, which again multiply be- 

 fore their metamorphosis into the plant, unless we rather regard them as 

 gonidia, and therefore as larvae, — where an undeveloped animal (larva) 

 should produce by asexual generation a multitude of individuals like itself, 

 which, no matter whether in the first or a later generation, would become 

 capable of going through the metamorphosis not completed by the latter, 

 in which case, consequently, the metamorphosis w ould appear, not as asso- 

 ciated with repro(kiction, but merely as a transformation of a being; — this 

 we regard as an ordinary metamor])hosis with multiple larva-generations. 



§ See Leuckart, Siebold u. Kolliker's Zeitschr. Bd. iii, p. 1/0 (1851), 

 and Article * Zeugung,* /. c. supra. 



