474 THE AMERICAN NATURALIST. [You XXXIX. 



zoological standpoint since it bears only indirectly upon the 

 material of these papers. Zoologists have, however, discussed 

 critically Strasburger's suggestions (see Wilson, : oo, p. 275, 

 and Hacker, '98, p. 101). The difficulties of accepting this 

 view of a possible antithetic alternation of generations in animals 

 seem insurmountable. In the first place there is not the 

 slightest evidence of antithetic alternation of generations in the 

 Metazoa or for that matter anywhere in the animal kingdom. 

 The examples of alternation of generations which the zoologists 

 present among the Ccelenterates are all illustrations of homolo- 

 gous generations derived from buds. There is no indication of 

 spore formation comparable to the process in the higher plants, 

 so far as I am able to judge, in any group of animals. And also 

 there seems to be accumulating evidence of reduction phenomena 

 previous to the development of sexual cells in the Protozoa 

 which is essentially of the same character as in the Metazoa 

 (see Wilson, : oo, pp. 227, 277, and Calkins, :oi, p. 233). It is 

 very interesting and remarkable that reduction phenomena 

 should show the same order of events in animals and plants and 

 the facts should be clearly recognized. But I cannot follow 

 those botanists who carry over to the animal kingdom the 

 phylogenetic conclusions which are so clear in plants. The 

 remarkable agreement of the events of sporogenesis in plants 

 with gametogenesis in animals appears to me likely to prove 

 only another illustration of similar biological phenomena which 

 have evolved independently of one another, an illustration com- 

 parable with the independent origin of sex, of heterospory, and 

 probably even of the sporophyte generation itself (involving the 

 processes of sporogenesis) in various groups of the plant king- 

 dom. 



We have considered this comparison of reduction phenomena 

 in plants with animals chiefly to emphasize the clear cut mor- 

 phology of the process as understood by the botanist. It does 

 not matter how close the events of sporogenesis may come to 

 those of gametogenesis in the higher angiosperms, the whole 

 background of plant phylogeny, which is wonderfully clear as a 

 whole, shows that reduction phenomena are the product of the 

 asexual generation. It represents, as Strasburger has so well 



