SENSIBILITY. 21 



our specific senses appear in the aggregate to have some connec- 

 tion with our general sensibiHty, and a most interesting study it 

 would be for all students of psychology to investigate this 

 subject. 



Another interesting branch connected with sensibility is to 

 study the evolution of this mysterious force or phenomenon. 

 Beginning with the minute organisms of plant-life, we naturally 

 press on into the higher regions of animal organisms, studying, as 

 we proceed, the action of unicellular matter, and observing the 

 gradual expansion of sensibility as we ascend in the scale of life. 

 The conglomeration of cells, the division of labour, the appear- 

 ance of special function, are all noteworthy. Then, from uncon- 

 scious sensibility, we proceed to conscious sensibility, eventually 

 finding ourselves landed in the mysterious region of a human 

 brain. Very interesting and instructive it is to begin with the 

 sub-kingdom Mollusca, taking, for example, the Ascidian of the 

 type Tiinicata, whose life-relation with the external world is very 

 simple indeed, the nervous system being very rudimentary and 

 consisting of simple small ganglia, which receive branches of 

 nervous filaments from the tentacles that guard the orifice of an 

 oval-shaped funnel, giving off outgoing filaments to various parts 

 of its muscular sac, to the alimentary canal, and other internal 

 organs. In this low form we have also those pigment cells in 

 which a rudimentary visual function is supposed to exist, being 

 situated in very close relation with the solitary ganglion. We pass 

 along to the Brachiopods, which are amongst the oldest and most 

 widespread representatives of the group to which they belong. 

 They are very similar to the Timicata in their visual organisation, 

 which is somewhat complex, yet no definite sense-organs have 

 been detected. 



Ascending the scale we get amongst the Lamellibranchs, 

 which appear to be the most complex mollusca known. Their 

 sense-organs being keen and highly-developed, they are endowed 

 with remarkable powers of locomotion. Some of the special 

 senses are undoubtedly represented amongst the . headless Mol- 

 lusca. Thus, the Pecten, Pupa, Spondylus, and Ostrcce are in all 

 probability possessed of tactile appendages. The functions found 

 in such organisms are distributed in a remarkable manner, though 



