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somes, would be too improbable and fantastic to consider. The 

 diploid and haploid relation must have arisen in the first instance, 

 it seems fair to say, either through the doubling of the original 

 ancestral number in the fusion of tvvo gametes or through the 

 halving of the original number in sporogenesis. If the diploid 

 condition arose through the fusion of two gametes, then any 

 phase or generation continuing it would be an "antithetic" 

 generation under the definition adopted by Dr. Fritsch. If, 

 on the other hand, the haploid condition first arose through the 

 halving of the original ancestral number, then any phase or 

 generation continuing it would escape technical conformity with 

 the definition of an "antithetic" generation, but would the 

 relations of the two phases be really different? Would not the 

 haploid gametophyte be "intercalated" instead of the diploid 

 sporophyte? Probably Dr. Fritsch and other supporters of the 

 homologous theory would reply that the gametophytic generation 

 would not be in itself a new intercalation under these circum- 

 stances and that the only new thing about it would be its sudden 

 change from a diploid to a haploid condition owing to a shifting 

 of the reduction in chromosome-number from gametogenesis to 

 sporogenesis. Dr. Fritsch, noting that the reduction in chromo- 

 some-number occurs in some algae at gametogenesis, in others 

 at the first division of the fusion nucleus, and in others at sporo- 

 genesis, evidently regards this as a cytological character of no 

 particular phylogenetic significance. And with the amount of 

 evidence now at hand it seems just about as difftcult to prove 

 him wrong as it would be to prove him right! 



The writer of the suggestive paper under consideration regards 

 the origin of the almost wholly dependent sporophyte of the 

 Bryophyta as difTerent from that of the soon independent spor- 

 ophyte of the Pteridophyta, calling the alternation in the former 

 antithetic and that in the latter homologous or rather "pseudo- 

 homologous" — a conclusion that may impress many of his 

 readers as being somewhat forced in view of the marked morpho- 

 logical and physiological similarities of these two groups of 

 sporophytes in the younger stages of their development. 



In the case of the tetraspore-bearing red algae, whose diploid 



