86 Scientific Proceedings, Royal Dublin Society. 



In many cases the periodic phenomena ultimately die out under 

 new influences, like the oscillations of a body in a viscous medium ; 

 in others when they seem to be more deeply rooted in physiological 

 conditions they persist. It is possible, however, that in the span 

 of years allotted to the higher organisms new conditions, such as 

 civilization, may gradually effect a change. 



However this turn out, the " length of life is dependent upon 

 the number of generations of somatic cells which can succeed one 

 another in the course of a single life, and furthermore the number 

 as well as the duration of each single cell-generation is predestined 

 in the germ itself." Such is the view which Weismann cautiously 

 favours.' Although it is perhaps useless to try to penetrate the 

 mystery, it seems, however, conceivable, as regards the means by 

 which the germ regulates the number and disposition of the cells 

 constituting the completed individual, that an initiating configu- 

 ration, followed by a very stable train of events, might be sufficient 

 to account for the persistence of the form of a species even under 

 certain variations of conditions. There are appearances of " trial" 

 in embryological development ; and it seems hardly more requisite 

 to ascribe to the germ the degree of directiveness necessary to 

 regulate the disposition of the parts of the completed individual 

 than it is to assume that the complexity of modern organic develop- 

 ment was prefigured in the originating unicellular form, if indeed 

 such has been the course of evolution. The " struggle among the 

 parts" once originated, the mutual adjustment might proceed 

 along lines of narrow possibilities till final equilibrium was 

 attained. 



And from this point of view it is hard to see any grounds for 

 assuming the complete isolation of the germ ; but, on the contrary, 

 we might well suppose influences upon the body, oft repeated, 

 transmitted to the germ plasma through the intermedium of the 

 colonists composing the complex organism. For similarly, we can 

 easily see how an important adaptive alteration arising in any 

 particular higher species might set up such a train of events occur- 

 ring among other organisms as would ultimately result in the 

 modification of the most lowly organism. So that if the events of 

 evolution were to occur anew this lowly organism might give rise, 



J "Life and Death " ; " Biological Memoirs," p. 146. 



