118 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



Exposure was experienced by all and included, besides great phys- 

 ical exertion, constant wetting from wading streams, often above 

 the waist and every hour of the day and from drenching rains 

 interspersed with periods of hot sunshine. 



The conditions did not require the presence of malaria trans- 

 mitting Anophelines and it is very clear that they played no part 

 in causing the malaria from which the men suffered. 



It seems to me that the situation closely parallels the one de- 

 scribed b3^ Doctor Lutz, as to character of forest, of men employed, 

 conditions of work and mosquitoes involved, and that probably in 

 that situation, as certainly in the one I have just described, the 

 agency of forest-breeding anophelines in causing the occurrence of 

 malaria may be safely excluded." 



The remainder of the evening was devoted to the following paper 

 by Dr. Hopkins and the discussion which ensued. 



DISCONTINUOUS GEOGRAPHICAL DISTRIBUTION. 



BY ANDREW D. HOPKINS, Bureau of Entomology. 



The discontinuous geographical distribution of animals and 

 plants is a subject of special interest and importance to the taxon- 

 omist, the ecologist, the investigator of technical and economic 

 problems, the student of geographical distribution and of the 

 broader questions of evolution. If the same species or the same 

 genus is established in many widely separated areas of the same 

 country or continent or in the countries of different continents, we 

 want to know something about the controlling factors which have 

 brought it about. 



I seems to me that the greatest difficulty to be met with in any 

 comprehensive consideration of the subject from published data is 

 the wide range of difference in the interpretation of specific distinc- 

 tion by taxonomists. There is often a marked difference of opin- 

 ion on this fundamental question among those who work on the 

 same group, but, when we consider the great difference in the inter- 

 pretation of the range or limits of specific distinction among special- 

 ists in entomology or zoology, or in the entire field of biology, the 

 complications in the difficulty of determining a reliable basis for 

 comprehensive study or conclusions is overwhelming; in fact is 

 prohibitive of reliable results. The genus of one author becomes a 



