app. METHODS OF EMBEYOLOGICAL EESEAECH 581 



beyond which it is mere waste of time to push observation. In all 

 biological observation the limit of probable error is particularly high yet 

 this fact is peculiarly apt to be ignored and it is no unusual thing to find 

 dimensions or other numerical data stated to three or four places of 

 decimals when anything beyond the first place is worthless for the reason 

 indicated. 



To secure accuracy of observation not merely training and experience 

 in the art of observing is needed but also a proper psychological outlook : 

 the observer must be able to take a completely detached point of view and 

 must ever be on the watch to guard against some particular hypothesis or 

 preconceived idea causing actual error instead of fulfilling its proper 

 function of keeping the powers of observation tuned up to the highest 

 pitch of alertness. 



The whole spirit and aim of scientific investigation is directed towards 

 the seriation of facts and the devising of general expressions or formulae 

 which unite them together. In this it contrasts with the more primitive 

 state of mental development which observes isolated phenomena, noting the 

 differences between them but blind to the common features which link 

 them together. In embryology as in other departments of knowledge the 

 able investigator sees the general principles which run through and 

 organize the masses of detail : he interests himself in discovering the 

 likeness which is hidden under superficial difference ; he is constructive 

 not destructive. 



In this volume embryology is treated as a branch of morphology but it 

 must be borne in mind that morphology and physiology are inseparably 

 intertwined. The living body whether of an embryo or an adult is above 

 all a piece of exquisite mechanism fitted to live and move and have its 

 being, and to ignore this is to make morphology as sterile and as misleading 

 as would be the study of machinery apart from the movements and 

 functions of its various parts. More particularly in attempting to delineate 

 the evolutionary past of an organ, or set of organs, speculation must 

 always be rigidly controlled by the reflexion that at each phase in 

 evolution it must have been able to function. 



When at length the stage is reached of putting results into form for 

 publication the first thing to aim at is absolute clearness of expression. 

 It must be remembered that clearness of language and clearness of thought 

 are closely interdependent. Sloppy obscure language means sloppy 

 obscure thought. The greatest care should be taken in the correct and 

 precise use of technical terms. Argumentation in regard to scientific and 

 other matters is, when the disputants are equally well informed, due as a 

 rule to some word or expression being used in slightly different senses. 

 Elegant literary style, however desirable, must always be subordinate to 

 clarity and precision of language. Indeed actual harm is sometimes 

 done to scientific progress by the writer whose literary skill carries away 

 not merely himself but others of uncritical and impressionable mind. 

 Scientific problems are eventually settled not by skill in dialectic but by 

 increase of knowledge. 



As a rule the proper presentment of an embryological thesis involves 

 pictorial illustration. In this the elaborate coloured lithographs of former 

 days may conveniently be replaced to a great extent by simple line or 

 half-tone drawings in India ink or process black which can be reproduced 



