Vol. XXV] ENTOMOLOGICAL NEWS 1 1 



forms and individuals that compose this flora and fauna, but 

 also that we are able to follow out in sequence all the lines of 

 their issue through a period of a few millions of years. What 

 would be the result of our observations in such case? It is 

 certain that we would see many forms drop out, we would see 

 many new ones arise, we would see great variations in some 

 and less variation in others, we would see some persist in nearly 

 their original form ; but most important of all from a taxono- 

 mic and phylogenetic point of view we would witness the pro- 

 duction of hordes and multitudes of transitional individuals 

 and forms that would quite effectually clog any known system 

 of classification, were they assembled with the typical forms 

 in their entirety. At any given time in the production of these 

 transitionals, the living residue would show plainer lines of 

 separation, but specific and other limitations among them would 

 not be amenable to current methods. These conditions are 

 actually exemplified today in certain young stocks inhabiting 

 favored regions. There are stocks of Muscoidea and Com- 

 positae in the Andean montanya whose progenitors have al- 

 most certainly been in that region or an equally favored con- 

 tiguous area for the past two or three millions of years, and 

 their living forms in many instances exemplify the conditions 

 just mentioned. While this region is probably the most highly 

 favored in this respect in the world, it is certain that many 

 other regions exist both in and out of the tropics where similar 

 conditions are exemplified by these and other young stocks. 

 Many muscoid groups exhibit today in various parts of the 

 world so many transitional forms and individuals that we have 

 long been unable conveniently to classify them. Yet we know 

 that these groups have already lost many of the transitional 

 forms, together with immense hosts of transitional individu- 

 als, that arose during their evolution up to the present time. 

 What conclusion can we draw from these facts? Simply that 

 there exist in nature, among groups of young stocks under- 

 going active evolution, no well defined or fixed species limits ; 

 but that there certainly exist aggregations of individuals ob- 

 serving some general specific bounds which suttice to meet the 



