No. 463.] STUDIES ON PLANT CELL. VI. 473 



The speculative possibilities of a suppression of a sexual gen- 

 eration and the assumption of sexuality by an asexual phase 

 were clearly in the mind of Strasburger when he suggested 

 ('9/j.b, p. 852) the possibility that the two mitoses characteristic 

 of oogenesis and spermatogenesis in animals might signify the 

 remains of a former sexual generation now entirely suppressed 

 in the Metazoa. This suggestion was based on the striking 

 similarity of the events of sporogenesis in plants to those of 

 gametogenesis in animals and on the history of sporogenesis as 

 shown in plant phylogeny. This history is remarkably clear and 

 there can be no question but that the phenomena of sporogenesis 

 have developed as the result of sexual processes and are always 

 associated with an asexual generation (sporophyte). It is also 

 clear that the ancestral primitive sexual generation (gametophyte) 

 h:is steadily degenerated until now it is almost lost in such 

 embryo-sacs as include the two mitoses of sporogenesis within 

 their history. If the sexual generation should become entirely 

 lost the life history of a higher plant would present the same 

 features with respect to the period of chromosome reduction as 

 that of an animal : there would be but one organism, the homo- 

 logue of the sporophyte which would produce gamete nuclei with 

 reduction phenomena previous to gametogenesis just as in- ani- 

 mals. Several authors have expressed views similar to Stras- 

 burger's suggestion ('94-b, p. 852) or carried the speculation even 

 farther than he. Beard ('95a, p. 444) along these lines of argu- 

 ment combined with conclusions from Bower's ('87) studies on 

 apospory, announced a belief that " Metazoan development was 

 really bound up with an antitJietic alternation of generations." 

 Lotsy (:O5, p. 117) expresses unequivocally the view that the 

 animal body represents an asexual phase (2x generation) and that 

 the sexual phase (x generation) is confined to the sexual cells. 

 Chamberlain (:c>5) simultaneously with Lotsy and in much 

 greater detail presents a comparison of the phenomena of sporo- 

 genesis in plants with gametogenesis in animals tracing the 

 resemblance in the events of chromosome reduction step by step 

 and states his belief that "animals exhibit an alternation of gen- 

 eration comparable with the alternation so well known in plants." 



This is not the place to consider this theory in detail from a 



