i/O GEOLOGICAL BIOLOGY. 



from the parent ; this is called budding, from its similarity to 

 the mode of budding in vegetable growth. 



III. This budding process may proceed within the parent 

 individual when separation takes place by an act of expulsion, 



Odd (SO 



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Fig. 45. — Agamogenesis by internal budding, in which the young germ is formed within the body 

 cavity of the parent, and when complete is suddenly expelled as a free individual. 



suddenly instead of gradually, which gives a third type of 

 agamogenesis, as may be illustrated by the diagram Fig. 45. 



In this case the offspring comes forth immature in develop- 

 ment, but complete in organization. All three of these modes 



(g5 ^ ^ ^ ^'° 



Fig. 46. — Monoecious gamogenesis. Sex differentiation, represented by the symbols A male, + 

 female, taking place within the parent individual (a(, the several steps consisting of union of 

 the two elements (3), development of the germ (<,-), its discharge (d e) and becoming a free 

 individual, the parent retaining its integrity (/). 



of generation are called agamogenesis, because there is gen- 

 eration without sex differentiation. 



Gamogenesis. — Ganiogoicsis is that mode of generation in 

 which distinction of sex is accomplished in the individuals be- 



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Tig. 47. — Dioecious gamogenesis. In this mode of generation sex differentiation has taken place 

 before the individual is complete, and co-operation of two distinct individuals is essential to 

 each act of generation {a a'). Separate organic elements are developed in the sex individuals 

 ibb'): the spermule is extruded from the male individual (c i 21, is brought into contact with 

 the ovule (3 c'), the two elements unite (r/), segmentation and development of the ovum iey) 

 take place, the ovum is -developed as a dependent individual until it is capable of independent 

 existence, when it is extruded and set free (g x and 2) either as a male or as a female individual 

 (^ 2). 



fore generation begins. Gamogenesis may (IV) be nioua'cious, 

 in which case the sex differentiation has proceeded only so far 

 as to differentiate the organs within the body of the individual 

 organism, each individual developing both of the sexual ele- 

 ments. This mode of genesis may be represented by Fig. 46. 



