CAUSE OF HEREDITY 297 



ials for providing- the young individual with a case is an 

 act of preadaptation to an end, not present but remote 

 This act, therefore, has all the marks of an instinct. Fur- 

 ther the instinct of the difflugia exhibits great precision, 

 for the difflugia not only knows how to distinguish at the 

 bottom of the water the material available for its purpose 

 but it takes only the quantity of material necessary to 

 enable the young individual to acquire a well built case ; 

 there is never an excess. 



"It is interesting to note that the difflugia does not act 

 differently from animals possessing more highly compli- 

 cated organization and endowed with differentiated nerv- 

 ous system, as for instance, the larvae of Phryganids, 

 which form their sheaths from shells, grains of sand or 

 minute slivers. We shall not regard it as strange, per- 

 haps, to find so complete a psychology in the history of 

 lower organisms when we recall to mind that agreeably 

 to the ideas of evolution now accepted a higher animal is 

 nothing more than a colony of protozoans. Every one of 

 the cells composing such an animal has retained its primi- 

 tive properties, giving them a higher degree of perfection 

 by division of labor and by selection. The epithelial cells 

 that secrete the nails and the hair are organisms per- 

 fected with reference to the secretion of protective parts. 

 Similarly the cells of the brain are organisms that have 

 been perfected with reference to psychical attributes." 



The cells described here by Mr. Binet are those still 

 living a single life in the water. This cell has the habit 

 of making a case around himself from the material at 

 hand. If no fine sand is at hand, he is able to use pow- 

 dered glass. A large number of other cells use the lime 

 and other material found in solution in water to make 

 their shells or covering. The actions of these single cells 

 are not instinctive as Mr. Binet suggests, they are con- 



