in EMBRYOTIC INDICATIONS 181 



pelvis for the support of legs, is amply 

 accounted for if we suppose that the 

 elements of the whole vertebrate Plan 

 were present, potentially, from the begin- 

 ning of the type, with an innate tendency 

 to appear in embryotic indications from 

 time to time. Both Owen and Mr. 

 Spencer, representing very different 

 schools of thought, have likened this 

 idea to that of the growth of crystals 

 along determinate lines, and bounded 

 by determinate angles. 1 Owen goes so 

 far as to call the imagined initial struc- 

 tures by the name of " organic crystal- 

 lisation." Although there is a danger 

 in passing, without great caution, from 

 the inorganic to the organic world, yet 

 this is a general analogy which is a real 

 help to thought. The almost infinite 

 complication of even the simplest organic 



1 Principles of Biology^ vol. ii. p. 

 Physiology, vol. iii. p. 8 1 8. 



