I now understood that here was a very wide field for further exploration; as. 

 however a long series of papers: my plancton work, many papers relating to the 

 biology of freshwater insects, and the bathymetrical explorations of the Fureso- 

 district first had to be carried out, I could only at rare intervals get time for these 

 observations during the 10 years from 1905 to 1915. Still the mosquito studies 

 were not quite laid aside, and in 1916 a more thorough study of the mosquito 

 larvae and their biology began. In 1912 the first volume of the great work of Howard, 

 Dyar and Knab relating to the mosquitoes of North and Central-America appeared; 

 the volume did not reach me before 1916. I immediately saw that all my above- 

 named more cursory conjectures were indeed correct, but also, that if published 

 they could not be regarded with any really new interest. 



In the time from 1910 — 1920 a series of shorter papers, dealing with the 

 biology of the European species, appeared, and the biological facts, mentioned by 

 the American authors, were generally corroborated by the European ones. In my 

 opinion this literature very often by no means comes up to the standard which should 

 be exacted for scientific work. 



After brief reflection I resolved that I would carry to an end my own studies 

 in spite of the whole American and European literature, and moreover that during 

 the study I would not take the slightest notice of it. My leading scientific views 

 were the following. 



From a purely scientific point of view, I have always regarded the question, 

 who first made a biological observation as a matter of sublime indifference. It 

 must never be forgotten, that even with regard to biological observations which 

 can only rarely be committed to paper with the same convincing exactness as an 

 anatomical structure, the exact apprehension of a given fact can only be acquired 

 through repeated observation. It is further of the greatest significance that the 

 biological observations are tested by different scientists and in different latitudes; 

 only in that way can our suppositions and hypotheses be registered among real 

 scientific facts. It must further be remembered that the study of Nature must always 

 begin with the slightest possible literary ballast. He who has first crammed his 

 head with all that has been written upon a subject, will at the moment of observa- 

 tion, when standing face to face with Nature, soon understand that his whole learning 

 is only felt as a burden and restricts his power of observation. I for my own part 

 have always been of the opinion that it is exactly the smallest equipment of human 

 knowledge which gives the greatest peace in my studies, creates the scientific 

 sovereignty over observations and thoughts and — as far as possible — moves the 

 milestones of time nearer to the borders of eternity. 



Having used the neighbourhood round Hillerod for more than twenty-five 

 years for my studies relating to the freshwater organisms, and often visiting the 

 hundreds of temporary ponds which were scattered within a radius of about 7 kilom. 

 over the country, especially in the forest, I had a rather extensive knowledge of 

 these ponds; having often hatched larva material from many of these ponds, I 



