58 Instinct and Intelligence 



becoming adjusted to their environment. In 

 the following pages we shall show this adapta- 

 tion between structure and instinctive processes 

 in those classes of beings which succeed the 

 Hydromedusa in the ascending scale of 



animals, viz., the 

 Echinodermata, in- 

 cluding star-fishes ; 

 the Annelida, to 

 which worms be- 

 - long; and lastly 

 the Arthropoda, 

 including crus- 

 tacea, such as cray- 

 fish and insects. 

 A typical star- 



FIG. 8. Diagram of the nervous system gU (Ficr R\ DOS- 

 of a star-fish, a, central nerve-ring sur- V >' 



rounding the mouth ; b, peripheral SCSSCS 3 Central 

 nerves of the arms. 



body from which 



five radiating arms extend outwards; on 

 their upper surfaces are numerous cal- 

 careous nodules supporting short spines. 

 Between these nodules there are a number 

 of processes or stems terminating in 

 pincer-like structures, worked by muscular 



