II] THE BEACH AND ROCKS 25 



Ulothrix may be extended to other plants as well. 

 It may be stated as a general hypothesis that 

 primitive life was aquatic, and certainly one of its 

 forms, if not indeed a general form of it, was 

 free-swimming. The quiescent stage with encysted 

 protoplasts characteristic of the vast majority of 

 plants now living was probably derivative in many 

 cases, and perhaps in all, and owed its origin to 

 the convenience which it offers for protection, as 

 well as for self-nutrition and growth. If this be 

 true, then it is the derivative condition which we 

 commonly recognise as the "plant." 



A second point for consideration relates to the 

 origin of sexualit}^ It has been seen that two 

 similar gametes unite in Ulothrix to form the 

 zygote. There is no differentiation of sex, though 

 the fusion is of the same nature as where such a 

 distinction exists. It would thus appear that some 

 process of fusion of cells antedated in descent the 

 distinction of sex. Further, the general similarity 

 in origin and form of the gametes and the zoospores 

 cannot escape remark. It would appear as though 

 the gametes were attenuated zoospores, a view Avhich 

 accords with their origin by further subdivision from 

 parent cells similar to those which form the zoospores. 

 It is possible that the fusion in such forms as these 

 originated as a means of strengthening the attenuated 

 zoospores. Again, comparison with the Flagellates 



