THE ORIGIN OF FOREST-GROUPINGS. 229 



eral introduction of vaccination the proportion has been reduced 

 to less than one per cent. 



The next most dreaded and at present the most fatal of these 

 diseases is scarlet fever. In England, during the period already 

 named, 67 per cent of all deaths under five were due to this cause ; 

 while an analysis of the registration reports of Massachusetts 

 shows that two thirds of the deaths from this cause occur under 

 five years of age. 



Diphtheria is especially a filth-disease as well as a contagious 

 disease ; while the prevalence of each member of the class varies 

 greatly in different localities and different years, being largely 

 dependent upon certain unknown epidemic influences, which as 

 yet have not been brought under the control of man. 



THE ORIGIN OF FOREST-GROUPINGS. 



By the MAEQUIS DE SAPOETA. 



THE organic relations or homologies of structure, showing con- 

 nections of different beings with one another, which, in igno- 

 rance of their real bearing, were formerly made useful only for 

 the classification of animals and plants into natural groups, have 

 acquired a new significance since the doctrine of evolution has 

 been brought to bear ui3on questions of origin and of the progress 

 through time and space of living beings and their relations with 

 those beings whose former existence is revealed by paleontology. 

 The question whether there are evidences of affiliation of the 

 former by the latter, of a direct relationship, has received atten- 

 tion from students ; and, as one of the attempts to solve it, 

 we may mention M. Gaudry's essay on " The Links in the Ani- 

 mal World," in which the development of the mammalia through 

 geological times is investigated on the basis of the osseous frame. 

 A difficulty that has never been surmounted besetting the study 

 of the terrestrial mammalia with aerial respiration, arises out of 

 their power of changing their place, which, while it is limited by 

 geographical restrictions in the case of quadrupeds, is complete 

 with birds. It is easy to conceive that overlappings and general 

 irregularities have time and again been introduced into the com- 

 binations of groups of animals which any given country has suc- 

 cessively contained. By that fact alone, the new-comers of each 

 period, at points where we have not been able to observe their 

 ancestors in the country of their origin, have an air of having 

 risen suddenly and been preceded by nothing. 



This is not so much the case in the vegetable kingdom, and is 

 least so with its most eminent representative, the tree, particularly 

 the forest tree or the tree that has become social. It is true that 



