272 LEISURE-TIME STUDIES. 



that such things are, and when the spirit of " das rastlose 

 Ursachenthier " moves abroad in search of the well-springs 

 of knowledge. The cause-seeking tendency of these latter 

 days has been well illustrated in physical science in two 

 ways. Of these, the first is exemplified by the endeavours 

 of scientists to account for the origin of the varied species 

 of living beings, and for the causes in virtue of which the 

 existing order of living nature has been fashioned and 

 evolved. Then, again, the question of the origin of matter 

 and of the universe itself has largely engaged the attention 

 of physicists and geologists. Although the origin of living 

 beings and of the world they inhabit was long ago decided 

 according to the Mosaic interpretation, the spirit of scientific 

 inquiry has found abundant cause to reject the idea of 

 "special creation" and also that of the "six days" theory 

 when applied to the foundation and building of the universe. 

 The higher knowledge of to-day has issued its fiat against 

 the pure assumption and dogmatic assertion of yesterday ; 

 and now, taking nothing for granted, we " step forth into 

 the light of things," and accept Nature as our great teacher : 

 seeking, in the search after causes, not what is likely, not 

 what is probable, but only what is true. 



Amongst the multifarious phases and aspects which are 

 included in the general question of the manner in which 

 living beings have been produced, no study has received a 

 greater impulse than that of " embryology." This depart- 

 ment of science is that which traces the stages through 

 which the young animal passes in development, from its 

 earliest appearance in the germ or egg until it has attained 

 the features of its parent, and until it has assumed the form 

 or likeness of the adult. No branch of study presents a 

 greater fascination to the scientist; for in its pursuit he 

 seems to peer further into the causation of living nature than 

 when engaged in any other department of inquiry. It can 

 be well understood how absorbing must be the interest with 

 which Nature's wondrous process of building the frame of 

 a living being is watched, and how large a view one may 



