REPRODUCTION IN HIGHER CRYPTOGAMIA. 385 



dividing the life of each into two separate epochs, in which it 

 presents itself under two very distinct phases that contrast re- 

 markably with each other. Thus, the frond of the Marchantia, 

 bearing its antheridia and archegonia, is that which seems natu- 

 rally to constitute the Plant ; but that which represents this phase 

 in the Ferns is the minute Marchantia-like prothallium. On the 

 other hand, the product into which the fertilized Embryo-cell 

 evolves itself in the Ferns, is that which is commonly regarded as 

 the Plant ; and this is represented in the Liverworts and Mosses 

 by the Spore-capsule alone.* — We shall hereafter encounter a 

 similar diversity (which has received the inappropriate designation 

 of ' Alternation of Generations ') between the two phases in the 

 lives of Hi/drozoa, as well as in other Invertebrate Animals. In 

 some of the Hydrozoa it is the Zoophytic structure which con- 

 stitutes what is commonly regarded as the Animal, the free- 

 swimming medusoid buds by which that structure is reproduced 

 being inconspicuous : whilst in others it is the Medusa or generative 

 segment which attracts notice by its large dimensions, the earlier 

 Polypoid stage being only recognized when carefully sought for. 

 (See Chap, xi.) 



* For more detailed information on the Structure and Classification of 

 the Cryptogamia generally, the reader is referred to the Rev. M. J. Berke- 

 ley's " Introduction to Cryptogamic Botany ; " while the most recent 

 information on the Reproduction of the Higher Cryptogamia will be found 

 in Prof. Hofnieister's Treatise on that subject, published by the Ray 

 Society. 



C 



