IS93-J 73 [Hyatt. 
in the presence of similar stimuli, when no special structure has 
been originated, can thus be readily accounted for if one considers 
heredity to be one form of organic memory. 
When special structures have arisen through habit the reappear- 
ance of these structures in descendants at the same time or earlier 
does not ])resent the same difficulty that it seems to place in the 
path of other theories. On the contrary, this is one of the strong- 
est confirmations of what may be called the muemogenic hypothe- 
sis of heredity or mnemogenesis. 
In mnemonics it is the machine-like regularity of the succession 
of cause and effect, of one word begetting the next, that surprises 
the student, the recurrence in the mind of long forgotten words, 
languages, and scenes, either in the recurrence of some inciting 
cause or upon the removal of interfering causes, as in the recurrence 
of youthful reminiscences in aged persons. Mnemotechnics as 
embodied in the various systems which have been devised to culti- 
vate the memory consists essentially in the habit of forming a chain 
of associated ideas or words leading up to the word or thought to 
be recalled. 
If characteristics were inherited irregularly there would be no 
parallel between the functions of memory and heredity, but the 
precision of the succession of hereditary characters in the develop- 
ment of the individual is precisely in accord with the theory of 
mnemogenesis. 
Even reversions that may be supposed to be purely sporadic 
do not oppose any serious obstacle, since there must always be 
latent hereditar}- mnemism in the cells and organs ready to mani- 
fest itself whenever more recently acquired characters are pre- 
vented from being developed in their proper succession. This is 
the most frequent form in which reversions are found among 
Ammonitinae. 
One of the greatest recommendations of this theory as a work- 
ing hypothesis, besides its plausible ai^plication to the explanation 
of such difficulties, is that it does not oblige us to begin as in a 
corpuscular theory by assuming a:i unprovaljle constitution of the 
germ plasm and an equally unprovable, and also in this case, 
inconceivable mech.inisni in the body by which specimen samples 
of these germs are attracted and finally concentrated from all parts 
into the spermatozoa and ova of every zoon. 
