RECENT WORK ON MOSSES AND FERNS. 361 



Klebahn, " Studien iiber zygoten," Pringsh. [ahi-b., xxii., 

 p. 415, etc.). 



Whatever the details of the process of reduction may 

 be, and we must wait for extended and direct observations 

 to supply them, it would seem probable that the divisions 

 of the zygote in the Confervoideie are connected with the 

 process of reduction, and perhaps owed their origin to the 

 necessity for such a change. Their existence appears to 

 have supplied the material upon which evolution has 

 worked, so as to result in one of the most surprising pheno- 

 mena in the whole organic world, — I mean the alternation 

 ot generations in the Archegoniata^. For we learn by 

 comparative study to believe it probable that the originally 

 simple neutral generation became elaborated into the exten- 

 sive body of the sporophyte ; a stage was thus intercalated in 

 the life-cycle, and becomes more prominent as the series of 

 archegoniate plants is reviewed in ascending order ; the 

 progression culminates in the final triumph of the 

 neutral generation as it is seen in the hiohest flowerino- 

 plants. 



The circumstances which led to the gradual advance 

 from the few neutral cells which result from the division of 

 the fertilised ovum as in the Confervoid Alga; to the larger 

 neutral generation of the Bryophyta (sporogonium), then to 

 the independent and still more complex sporophyte of the 

 Pteridophyta, seem to have been as follows : Fertilisation 

 is in all these organisms effected through the agency of 

 water ; since yi aquatic organisms this may take place at any 

 time, increase in number of individuals may take place with- 

 out intermission ; and this may, and in some cases apparently 

 does, meet the needs for maintenance of the race. But if 

 such organisms migrate to the land, escaping thereby it 

 may be from inconvenient competition, or those conditions 

 being in other ways more favourable, a check would at 

 once be imposed upon unlimited sexuality ; since water 

 would only be present at intervals of rain, dew, or submer- 

 sion, it would only be possible then to carry out the sexual 

 process. As against the restriction of increase thus imposed, 

 we may recognise the increased number of divisions succeed- 



