THE I V0L1 TION OP Till. \l RVO 





anemone No. 2 of Pig. 201 . In the jellyfish, which in contrasl to the 

 anemone is a free moving animal, we find thai the receptors are more highly 

 specialized and, therefore, much more sensitive, and thai tin- impulses which 

 they receive are -transmitted to a more definite nerve network, capable doI 

 only of conveying the excitatory process from one pari <>t' the animal to an- 

 other, Km also of imprinting on the impulse ;i characteristic rhythmic ac- 



i. 



5|)ent)c 



5ea anemone 



Simple form in 

 earthworm 



i e Addition of 



association neurons 

 in earthworm 



l. Diagram to show gradual e> iti '•'»' cell 



and in the »| '■ epithelu 



■ .11 in tbf m u | in a Kan k - 



mi simple form miii in the earth.. M - 



invertebr. 



tivity which brings aboul the contraction <»t' the bell ami the sw imming mo 

 m. 'lit hi' the animal. 'I'll.' network now assumes the function «>t' an n 

 as well as a transmitter of imputa 



So far the adjuster is an extremely simple structure, ami it is possible 

 that the effector ami receptor organs are directly com by fil 



running through it. When we come t.> the segnu nted ini 



