WIS] Alterxatiox Axn Pakthexogexesis ix Padixa 93 



ished. The test made in 19 IG already referred to, corroborates the 

 result of the cultures. The first lot of eggs frpm the female plants 

 gave sporclings which continued to develop during the course of the 

 experiment. Tliese, as has been said, were manifestly fertilized eggs, 

 which remain attached to the parent plants for a remarkably long- 

 time, since the next lot, obtained about one week later and after agi- 

 tating the plants sufficiently to dislodge the retained eggs, began 

 growing as before, but all disintegrated after dividing into cells vary- 

 ing in number from 2 to as many as 50 or more. 



Xow, although in Padina and the Dictyotaceae generally nnferti- 

 lized eggs germinate, according to the writer's interpretation of the 

 above described experiments, in Padina at any rate, such germinating 

 eggs invariably perish before reaching maturity. Comparing this 

 case with the many cases of artificial parthenogenesis, it is unlikely 

 that there can be any real differences between such cell division when 

 inaugurated naturally and when artificially induced. ]f the former 

 fail to mature, it would seem quitely probable that the latter must 

 likewise fail, and from the same inherent difficulties, and therefore 

 before artificial parthenogenesis is accepted in the sense in which it 

 is ordinarily understood, it will be necessary to rear mature individu- 

 als from eggs containing the reduced number of chromosomes. 



Sr.MMAUY 



The results above given in detail may be very briefly sunniiarized 

 as follows : 



(1) Tetraspores produce only male and female plants, '{"he num- 

 bers are a])])roximate]y equal even when the spores are from the same 

 })lant and grown on the saiue shell. Sex is therefore predctcruiiurd. 

 probably, in the reduction division of the tetraspore-mofher-ccll. 



(2) Eggs wlieu fertilized produce tetrasporic plants only. TIhtc 

 is thus an alternation of a sporopjiyte generation which is an entirely 

 distinct individual, with the gametophytic generation consi.sting "f 

 two scpanitc plants, the one bearing eggs the oth(>r sperms. 



