410 



W. K. BROOKS ON THE LIFE-HISTORY 



f Medusa X I Medusa <Eggs. 



( Nutritive Hydra f ' ) Jlfedwsa < Eqqs. 

 Nutritive Hydra X •J Blastostyle X { 



{ Defensive Hydra ' -^^ x ( Medusa < Eggs. 



\ Medusa <^ JEg'g's. 

 X 



r if ; w f Medusa <C Eggs. 



\ Medusa X \ . 



(Nutritive Hydra X 



X 



Nutritive Hydra X 



IX. PoDOCKYNE 



Egg = Planala =lioot X 



Nutiitive Hydra I Medusa < Eggs. 

 Blastostyle X { 



Defensive Hydra j „. ( J»/erf«*u < &/;/.«. 



^ to '" S(lX 1 Medusa <Eggs, 



C Medusa X { Medusa < Eggs. 



I J\ utriti ve Hydra \ Medusa < Eggs. 

 ■a X ■. Blastostyle X < 



( Defensive Hydra ,, 7 ., t Medusa < Eggs. 



J J ' Medusa X { , r i ^ t? 



\ Medusa <^.Lggs. 



C Medusa X i Medusa < E 99«- 



r Nutritive Hydra } \ Medusa < Eggs. 



Nutritive Hydra X ■! Blastostyle X < 



( Defensive Hydra 



Medusa <^ Eggs. 



i jueausa < js'/(/. 



( Medusa X I i, r , ^ it. 



( Medusa < A;/;/ 



X 



i Nutritive Hydra X 



X 



Nutritive Hydra f ~ ( 3fedwsa < £grgrs. 



Blastostyle X ■{ 



Defensive Hydra ,' , .. f 3/edwsa < £r/(/s. 



[ Medusa X { -xr i ^- -c 



L ( Medusa <^ i.;/;/s. 



( Nutritive Hydra ~ { Medusa < £>/*. 



Nutritive Hydra X < Blastostyle X -J 



( Defensive Hydra j ,,- f Medusa < iv/;/-'- 



It is very probable that future research will show that even this complex diagram is 

 too simple for some of the Hydromedusae, and that there is, in some eases, a secondary 

 alternation between the first generation of free medusae and those which are produced by 

 budding' from this generation. The life-history of these proliferous medusae has not been 

 studied, as they are seldom found near laboratories and appliances for research, but there 

 is reason to suspect that in some of them only those medusae which are budded from the 

 bodies of the medusa' of the first generation become sexually mature; and if future re- 

 search should prove this we should have still another alternation between the asexual 

 proliferous medusa? and their sexual descendants. 



In Hydractinia, the cormi of which are so similar to those of Podocoryne that a draw- 

 ing of one will correctly represent the other, the life-history begins to simplify itself by 

 the degradation of the sexual medusa into sessile buds, or reproductive organs, which, 

 however still retain traces of their former independent locomotor existence; traces which 

 have almost totally disappeared in Eudendrium and in many of the Campanularians. 



The life-history of Hydractinia may be represented as follows: 



