and its relation to that in the Animal Kingdom, 443 



result of a 'setting-back* [zuruck-greifen] to a very early stage 

 of development, of the asexual multiplication, which otherwise 

 mostly occurs only just before puberty, and then with variability 

 as to whether the puberty is subsequently attained or not, — or 

 after that epoch*. These themselves are not repeated (at least 

 not in the last generation), but others, ab origine different, are 

 produced — the asexual multiplication appears directly combined 

 with metamorphosis. Such is the case in Animals. 



In the Vegetable Kingdom, the observations of Pringsheim, 

 Cohn, and Thuret on certain Algaj, which are reported with some 

 confirmations in former pages (352-8), have demonstrated a pro- 

 cess of fecundation exactly resembling that of animals, completed 

 through immediate contact of spontaneously moving spermatic 

 (fecundating) corpuscles with a naked mass of germinal substancef 

 corresponding with the naked vitellus of the Worms. Without 

 contact with the former, the latter remains undeveloped, or its de- 

 velopment does not go on beyond the first step (commencement of 

 germination of the spore of FucusX) ; the contact, on the con- 

 trar}'', is followed by development, and either proceeds without 

 interruption, or, after definite periods of rest, with or without 

 intermediate forms (intermediate generations), onward to the 

 repetition of the sexual mother-plant. 



In the Mosses and Ferns (in the extended sense) we are ac- 

 quainted, in the spermatic filaments, with structures correspond- 

 ing exactly to the fecundating corpuscles of the Algae; here 

 also the germinal vesicle (the daughter-cell of the central cell of 

 the archegonium) is completely analogous to the germinal sub- 

 stance of the above : it requires for its further development the 

 influence of the spermatozoids, whose approximation to it has been 

 observed by Suminski, Mercklin, and Hofmeister (see pp. 348, 

 352). It may for the present remain as undecided here, whe- 

 ther the germinal vesicle about to be fecundated is, as Pringsheim 

 conjectures, a naked primordial cell, or, as Hofmeister states, 

 already possesses a cellulose membrane. The latter condition, 

 which would correspond to an ovum possessing a vitelline mem- 

 brane at the epoch of fecundation, would merely require that 

 the spermatozoids, to come into direct contact with the proper 

 vitelline (germinal substance) mass, should penetrate the enve- 



* In the case of Alcyonella, to be mentioned presently, we see it set 

 back to the rudimentary embryo. 



t Cell-contents without coating membrane ; " the contents enclosed by 

 this envelope (cellulose membrane) are the essential and original part of 

 the cell, indeed must be considered as the cell even before the enveloping 

 membrane is formed/' says Alex. Braun (' Verjiingung,' p. 166); and in 

 this sense I use, in the sequel, the expression ' primordial cell,' without at 

 all including in the conception the presence of a primordial utricle. 



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



