442 Dr. L. Radlkofer 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 after penetration 

 into the ovum in fecundation, whether it be a ferment or anj'^- 

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

 substance of which it is composed, and consequently that we 

 need not particularly wonder, if we should meet anywhere in 

 iiatux'e 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 cei'tain 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 X 

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

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



* Leiickart, Article ' Zeugung,' in Wagner's Haudworterbuch der Phy- 

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

 development of individnals from uufecundated ova of Daphnia, Talceporia, 

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

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

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

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

 (Thuret, Ann. des Sc. nat. 4 =er. ii". p. 204, 1854.) 



t I consider mystlf quite ju: tified in leaving unnoticed, as insufficiently 

 established, the single fuse, as yet contradictory of the above, of the occur- 

 rence of several embrj'os in one ovum in Planaria. The accounts given 

 bv Van Beneden of a subdivision of originally sim])le ova of Tubuluria and 

 Hydractinia into several smaller ova, each of \Aliich 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 everv 20-40 of the fecundated ova of the Gasteropodous 

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

 one sin£le embryo. [See on this point Ann. Nat. Hist. ser. 2. xix. pp. '6'6i}, 

 43i, and xx. p. "6.— A. H.] 



;|: Followmg Leuckart, we do not include in the conception of alterna- 

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

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

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

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

 gonidia, and therefore as larvfe, — where an imdeveloped 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 

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

 in which case, consequently, the metamorphosis would a])pear, not as asso- 

 ciated with reproduction, Ijut merely as a transformation of a being; — this 

 we regard as an ordinary metamorphosis with multiple larva-generations. 



§ See Leuckart, Sicbold u. KoUiker's Zeitschr. Bd. iii. p. 170 (1851), 

 and Article ' Zeugung,' /. c. siqjra. 



