366 'Journal of Comparative Neurology and Psychology. 



The dynamic theory proposes to view the organism as a correla- 

 tion of figures of activity in such a way that the behavior of the 

 animal as a whole is a resultant activity into which the elements 

 enter to a greater or less extent without complete loss of their 

 integrity. Energy or activity is of such nature that it is capable of 

 being individualized without losing the possibility of recombining 

 the whole. As motion may be rectilinear or curvilinear and 

 curvilinear or gyratory motion is capable of acquiring individual 

 modes as rectilinear motion is not, so activities corresponding to 

 elementary parts of the body may be compounded to produce re- 

 sultants without surrender ot their individuality or may be united 

 into a new progressive activity with a complete surrender of indi- 

 viduality, but the resultant will still be a true descendant of the 

 parent motions. Such analogies are important in the study of 

 development. 



As to chemical variation, this is but a special case of differences 

 in trajectory or figure among units of activity. Take for illustra- 

 tion familiar instances in organic chemistry which illustrate the 

 grouping of a number of minor complexes (molecules) into an 

 organic radicle forming the base of a series in which this con- 

 stant appears in varying proportions, groups of atoms behaving 

 like atoms in that they may be transferred from compound to 

 compound. Thus hydrocarbons having the general formula 

 CnH2n+smaybe regarded as hydrides of the radicle CrH^n + i, 

 so that 



methane .(CH^) — H = methyl (CHs), 

 ethane (CoHc) — H = ethyl (C2H5), etc. 



The assembling of series formed from such radicles, like the marsh 

 gas or the aromatic series, shows that a regular gradation of physical 

 properties accompanies the changes in proportions. (In our illus- 

 tration the properties of the members of the marsh gas series are 

 graded in accordance with constant additions of H2.) If the sug- 

 gestions offered above as to the nature of chemical union are 

 accepted, then the similarity in diversity giving rise to such series 

 or expressed more generally in the periodic law is not due to the 

 accumulation of different amounts of material bodies (which in 

 itself would, in fact, explain nothing), but to the composition of 

 forces by such constant increments as give rise to rhythmical 

 coincidences in form of such a nature as to produce the effect of 



