166 HABIT AND INTELLIGENCE. [chap. xiv. 



NOTE B. 



FORMATIVE AND MOTOR FUNCTIONS. 



I DO not know tliat it ought to be said that there is no gradation 

 Actions between the formative and the motor functions. The Forami- 

 in Forami- xiifera, and some other Rhizopods, put forth projections of the 

 once for- sarcode substance of the body, called pseudopodia, which are, at 

 mativeand least as to function, temporary tentacles. May not these be truly 

 homologous with the permanent tentacles of the Hydrozoa ? If 

 so, the putting forth and retraction of the pseudopodia, which, 

 are manifestly motor actions, are also to be classed as formative, 

 forming the transition from the formative to the motor functions. 

 What supports this conjecture is the fact, that in gromia the 

 pseudopodia are only formed at one end, but in amoeba they are 

 formed on any part of the surface of the body ; just as in hydra 

 the tentacles all form a ring round the mouth, but in some of 

 the compound Hydrozoa there are tentacles on various parts. 

 Dr. Wyville Thomson appears to share this view. He says : " I 

 am strongly inclined to regard cilia as locomotive pseudopodia, 

 and to consider them special to the sarcode [living but struc- 

 tureless] element." (Embryology of the Echinodermata, Natural 

 History Review, Oct. 1864.) Cilia are certainly in some degree 

 permanent organs. 



