28 



Mr. W. K. Brooks on the Origin of 



VII. EuTiMA : 

 Egg = Planula=Root X 



Nutritive Hydra X 



Nutritive HydraX 



Blastostyle ; 



Nutritive Hydra 



{Nutritive Hydra 

 Blastostyle ) 



Medztsa<:Ugg.<i. 

 Medusa-^ Eggs. 

 Medusa'^Eggs. 



1 Medusa<zEggft. 

 I Medusa<^Eggs. 

 I Medusa^^Eggs. 



In Podocoryne {Dysmorphosa) we have an extremely com- 

 plex life-history, which, however, is readily derivable from 

 one like that of Eutima as just given. There is a secondary 

 alternation between the root and the hydranths, as in Eutima^ 

 and the polymorphism between the hydranths is more special- 

 ized, as we find not only nutritive polyps and blastostyles, 

 but defensive polyps as well ; and as each of the meduste, in 

 addition to its sexual function, also possesses tlie power to 

 produce other medusa by budding, the number of sexual 

 animals which may be derived from a single e^g is unlimited. 



The following diagram represents the life-history of this 

 species, except that the first generation of medusse, like the 

 second, gives rise to reproductive elements : — 



VIII. PODOCOUYNE : 



Egg = Plan ula =■ 

 liout X 



I Nutritive Hydra 

 Blastostyle X 



Defensive Hydra 



1 Nutritive Hydra 

 Blastostyle X 



Defensive Hydra 



1 Nutritive Hydra 

 Blastostyle X 



Defejisive Hydra 



\ Nutritive Hydra 

 Nutritive Hydra X I Blastostyle X 



( Defensive Hydra 



! Nutritive Hydra 

 Blastostyle X 



Defensive Hydra 



I Nutritive Hydra 

 Blastostyle x 



Defensive Hydra 



( Medusa X 

 (^ Medusa X 



\ MedusaX 

 Medusa X 



Medusa X 

 (^ Medusa x 



r Medusa x 

 (^ Medusa X 



( Medusa X 

 \^MedusaX 



\ Medusa X 

 (, Medusa X 



\ 3Iedusa<::Eggs 

 ] Medusw^-Eggs 



\ Medusa'^Egggi 

 I Medusa<^Egg8i 



\ Medusa<zEggs 

 \ Medusa<^Eggs. 



\ Medusa<:Eggs 

 ] Medusa<^Eggs 



) Medusa<:Eggs. 

 ) Medusa<^Eggs 



I Medusa<:Eggs 

 I Medusa<^Eggs. 



I Medtisa<:Eggs 

 \ Medusa<^Eggs . 



j Medtisa<zEggs. 

 I Medtisa<'~Eggg. 



I Medusa<:Eggs. 

 I Medutin-=^~Eggs. 



I Medusa-^Eggs. 

 j Medusa<^Egg^, 



i Medusa<iEgys. 

 I Medusa<-Eggs. 



\ Medusa<:Eggs. 

 j Medusa-<^Eggs. 



