EXTRACT XXII. 



ON THE NOTOCHORD, AS A SKELETAL EVOLU- 

 TIONARY FACTOR. 



WHAT does the term notochord signify ? No answer to 

 that question has yet been vouchsafed to the most 

 "anxious inquirer," and the subject has to a great extent 

 been "shelved," or "hung up," waiting the advent of a 

 suitable time, and circumstances propitious, for the con- 

 sideration of questions considered devoid of all possible 

 practical advantage, but which may have an element of 

 possible scientific interest, sufficient to excite a " passing 

 notice." In the latter aspect of the subject, we feel called 

 upon to take it up, in order, if possible, to throw some 

 light, if it be only that of curiosity, upon it. 



To begin with, the history of its discovery is, so far as 

 we have been able to make out, comparatively recent and 

 has consisted of its topographical delimitation and the 

 recognition of its anatomical details, all of which is highly 

 informative to the student of embryonic structure and 

 valuable, as a " find," to the collectors of anatomical 

 archaeology and evolutionary survivals, but it does not 

 satisfy even mere curiosity, we therefore, feel impelled to 

 soliloquise for a little on its probable meaning, after, for 

 some time, regarding it as intently, as we have been able, 

 from the various aspects reachable from our individual 

 points of view. In attempting an explanation of its 

 nature, we would observe that its embryonic advent 

 seems, to us, to anticipate the process of skeletal building, 

 and to synchronise with the erection of the scaffolding, so 

 to speak, by the formative factors, in the great work of 



