HEREDITY. 453 



tive elements. It is evident that these and the other or- 

 ganic units of which the organism is composed possess 

 a memory-structure which determines their destiny in 

 the building of the embryo. This is indicated by the re- 

 capitulation of the phylogenetic history of its ancestors 

 displayed in embryonic growth. This memory has 

 perhaps the same molecular basis as the conscious 

 memory, but for reasons unknown to us, consciousness 

 does not preside over its activities. The energy which 

 follows its guidance has become automatic, and it 

 builds what it builds with the same regardlessness of 

 immediate surroundings as that which is displayed by 

 the crystallific growth-energy. It is incapable of a 

 new design, except as an addition to its record. 



Were all cells identical in characters, every one 

 would retain the 'structural record, or memory of its 

 past physical history, as do the unicellular organisms. 

 Evolution has, however, so modified most of the struc- 

 tural units of the organic body that none but the ner- 

 vous and reproductive cells retain this record, in 

 greater or less perfection. The nervous cells have 

 been specialized as the recipients of new impressions, 

 and the excitors of definite corresponding movements 

 in the cells of the remainder of the organism. The 

 somatic cells retain only the record or memory of their 

 special function. On the other hand, the reproduc- 

 tive cells, which most nearly resemble the independent 

 unicellular organisms, retain first the impressions re- 

 ceived during their primitive unicellular ancestral con- 

 dition; and second, those which they have acquired 

 through the organism of which they have been and are 

 only a part. The medium through which they can 

 receive such impression is continuous protoplasm. 

 Whether, in the higher animals, it is effected through 



