536 



REPRODUCTION OF HYDRA. 



Fig. 275. 



their cavity is connected with that of the parent, but at last the 

 communication is cut-off by the closure of the canal of the foot- 

 stalk, and the young Polype quits its attachment and goes in quest 

 of its own maintenance. A second generation of Buds is sometimes 

 observed on the young Polype before quitting its parent ; and as 

 many as nineteen young Hydrce in different stages of development 

 have been thus connected with a single original stock (Fig. 275). 



Another very curious 

 endowment seems to 

 depend on the same 

 condition, — the extra- 

 ordinary power which 

 one portion possesses 

 of reproducing the 

 rest. Into whatever 

 number of parts a 

 Hydra may be di- 

 vided, each may re- 

 tain its vitality, and 

 give origin to a new 

 and entire fabric ; so 

 that thirty or forty 

 individuals may be 

 formed by the section 

 of one. 



412. The Hydra 

 also propagates itself, 

 however, by a truly 

 Sexual process ; the 

 fecundating apparatus, 

 or vesicle producing 

 Sperm-cells, and the 

 Ovum (containing the 

 Germ-cell, imbedded 

 in a store of nutri- 

 ment adapted for its 

 early development) 

 being both evolved in 

 the substance of the 

 walls of the Stomach, 

 the former just 

 beneath the arms, the latter nearer to the lower end of the body. 

 It would appear that sometimes one individual Hydra developes 

 only the Male cysts or Sperm-cells, while another developes only 

 the Female cysts or Ovisacs ; but the general rule seems to be that 

 the same individual forms both organs. The fertilization of the 

 Ova, however, cannot take-place until after the rupture of the 

 Spermatic cyst and that of the Ovisac also ; so that the parent 



Hydra futca in gemmation ; a, month 

 c, origin of one of the buds. 



b, base 



