30 Dr. Wallich on Endogenous as distinct fn^om 



The view which I believe to be the true one is that the 

 remote ancestor of the hyclromeduste was a solitary swimming 

 liydra or actinula, with no medusa-stage, but probably with 

 the power to multiply by budding. I believe that tliis pelagic 

 animal gradually became more and more highly organized 

 and more perfectly adapted for a swimming life, until it finally 

 became converted into a medusa with swimming-bell and 

 sense-organs, developing directly from the egg without alter- 

 nation, but exhibiting during its growth the stages through 

 which it had passed during its evolution. After this stage of 

 development had been reached, I believe that the larva derived 

 some advantage from attachment to other bodies, either as a 

 parasite within other medusee or as what may perhaps be 

 called a semi-parasite upon other floating bodies, such as the 

 fronds of algaj ; and that it multiplied asexually in this sessile 

 condition, giving rise to other larvie like itself, all of which 

 became medusa?. 



I believe that the sessile or attached mode of life of the 

 larvas proved so advantageous to the species that it was per- 

 petuated by natural selection, and that the primary larva then 

 gradually lost its tendency to become a medusa, but remained 

 a sessile larva, giving birth by budding to other larvas which 

 became sexual medusge ; that the medusa-characteristics of 

 these secondary larvae were accelerated, and that the primary 

 larva gradually acquired at the same time the power to pro- 

 duce other larva3, which remained permanently, like itself, in 

 the hydra stage ; that in this way the sessile hydra-communi- 

 ties with medusa-buds and free sexual medusas were evolved ; 

 and that finally these communities became polymorphic, and 

 that the sessile habit proved so advantageous that the free 

 medusffi became degraded into medusa-buds or sexual buds 

 on the bodies of the sessile hydras. 



V. — Endogenous as distinct from Exogenous Division in the 

 Amaiban KJnzopods. By Surgeon-Major Wallich, M.D. 



I PROPOSE to show in this communication that whereas 

 endogenous division in the naked Amoeban Rhizopods is the 

 prime factor in normal reproduction, exogenous division, in 

 the majority of instances in which it is seen to take place 

 during microscopic observation, is merely a mechanical dis- 

 ruption of the body-substance into two or more separate 

 masses, produced accidentally by forces operating from 



