THE SCOPE OF ZOOLOGY 



studies, it might be possible to derive some conclusions as to the validity 

 of the hypothesis which has been made. 



In many scientific investigations, on the other hand, it is possible to 

 control the subjects under investigation and thus to conduct experiments. 

 For instance, if we wanted to learn about the method of inheritance of 

 ear position in dogs, we could breed dogs with erect ears to those with 

 drooping ears and, through a study of the ear position in the succeeding 

 generations, we could hope to determine the validity of any hypothesis 

 which had been made. Of course, observation and tabulation of re- 

 sults would be necessary where experimentation was used. In general, 

 it is possible to obtain results faster where experimentation can be used 

 in addition to observation than when we are limited to observation as 

 the sole method of study. 



When the data are analyzed it may be found that the hypothesis 

 which has been formulated will have to be discarded and a new one 

 proposed in its place, but the scientist must be very careful at this point 

 not to jump to conclusions and to wait until conclusive evidence has been 

 obtained before advancing any hypothesis to the status of a fact or even 

 a theory. 



Sometimes the word theory is used to describe an hypothesis which 

 has accumulated a considerable weight of evidence behind it, but which 

 has not reached the point of definite proof. There are some cases 

 where it is impossible to obtain final, conclusive proof, and the state- 

 ment must remain a theory indefinitely. Such scientific theories may 

 be very valuable in the advancement of scientific knowledge. We 

 should take care, however, to distinguish scientific theories from sci- 

 entific facts, for they are sometimes confused in the popular mind. 

 Take the subject of biological evolution, for example. Many phases 

 of this subject are known facts that can be proved to the satisfaction 

 of anyone who will take the trouble to investigate. On the other hand, 

 there are theories as to the mechanism of evolution and the extent to 

 which evolution has progressed in the past that have not been proved 

 and can never be proved. We should distinguish between these in our 

 thinking and not lump all statements about evolution into one category 

 or the other. 



The Scientific Method in Action 



These statements about the scientific method may be better under- 

 stood if we illustrate them with regard to an actual scientific problem. 

 Suppose, for instance, that you wished to investigate a problem of 

 mosquito reproduction — Is water necessary for the propagation of 



