322 JOHN BEARt), 



two courses would be open. Either we might shut our eyes to what 

 lay before them, and still continue to uphold and teach the simple 

 laws established by the researches of a century. Or, knowing the 

 science of embryology to be but something as of yesterday, we might 

 concede, that its laws, as based merely on our experience, were open 

 to revision, and even to repeal. 



Of tlie dogmas of embryology there is one which at the present 

 day takes first and last place, forms the beginning and the end of 

 most embryological doctrine. In a crude form the recapitulation- 

 theory has long held sway, notwithstanding its inability to cope with 

 and explain the mass of embryological fact already gleaned, and 

 gathered withal largely in its behoof. 



Explanations of embryological phenomena can only acquire the 

 status of laws when they are such as are applicable to all the facts, 

 the known ones and those also which become the property of the 

 science. When used merely as a working hypothesis, recapitulation 

 has often been of immense service, not so much by reason of any 

 positive results thereby gained in its favour as by stimulating scien- 

 tific inquiry. As the law of development, in the form given to it by 

 Prof. Haeckel and others^), it may be questioned whether its 

 effect has not been to retard the advance of knowledge. For, if re- 

 search be undertaken merely to find a series of pictures already 

 guessed at, it is conceivable, nay likely, that in many cases facts 

 which have no bearings on the points had in view, may be ignored 

 as of no value whatever, and thus their importance — and even the 

 most insignificant fact has some — may be lost to the science, at 

 any rate for a time. 



Of such facts some few at least of those recorded in the follow- 

 ing researches furnish instances in point. Some of them must have 

 met the eyes of various observers at different times during the last 

 twenty years. But, according to the tradition, the development of 

 the Vertebrate nervous system has hitherto seemed to proceed straight 



1) The so-called "law of Ontogeny" according to which every 

 embryo "climbs its own genealogical ti'ee, seeking its pedigree in the 

 course of its own development". With this hypothetical law the em- 

 bryological maxim '■'omne Organum ex organo'\ which forms the scien- 

 tific basis of comparative anatomy and also of an embryology of organs, 

 is not to be confounded. 



