444 Beard. — Reproduction in Animals and Plants. 
transformations in allied forms, observations on the first 
appearance of sexual characters in the vertebrate embryo, 
the attainment of the adult form of body, the formation of 
the definitive nervous system in the fish-embryo, and com- 
paring the appearance of these latter factors with the period 
of commencing degeneration of the transient nervous appa- 
ratus, it became evident that the initiation of degeneration 
was in association with a number of phenomena which could 
be nothing other than a metamorphosis. And it then began 
to dawn upon one that the development of a lower Vertebrate 
was in reality an alternation of generations in which the 
sexual form began to be formed upon an asexual foundation 
at a very early period. It was then recognized that the two 
could only co-exist as long as the sexual generation was, 
so to speak, merely dormant upon the asexual one, and that, 
as soon as the former began to manifest activities in its 
development, these led without fail to the suppression of the 
latter. Owing to complete want of homology between the 
parts of the two generations, as proved by their different 
nervous systems, and as further manifested by numerous 
types with larval development among the Invertebrata, it 
became obvious that Metazoan development was really bound 
up with an antithetic alternation of generations. This was 
the standpoint reached when I became acquainted with 
Bower’s researches and results on Apospory in ferns 1 . Then 
many things found their natural interpretation, for it was at 
once recognized that the conclusions previously arrived at 
pointed to a sort of Apospory in animal development. At 
the same time the problem of the nature of the reducing 
division intruded itself, thanks to a presidential address of 
Prof. Bower’s 2 in which Strasburger’s conclusions were dis- 
cussed. 
It seemed necessary to find the explanation of this in 
animals, if, as was more than suspected, there existed some 
1 Bower, F. O., On Apospory and allied phenomena. Trans. Linn. Soc. Ser. 
Bot., Vol. ii, Pt. 14, 1887. 
2 Botanical Society, Edinburgh. Nov. 1894. 
