RELATIVE INFLUENCE OF PARENTS. 241 



mucous or intestinal layer, are developed the epithe- 

 lial lining of the alimentary canal, and all its glandu- 

 lar extensions, such as the mucous, the gastric, and 

 intestinal glands, the pancreas, and the liver, also the 

 lungs and respiratory passages, and the urinary appa- 

 ratus, including the bladder, ureters, and kidneys." l 



From this outline of the origin of the different 

 organs in the development of the embryo, it will be 

 seen that the classification of organs made by Messrs. 

 Walker, Orton, and Spooner, is not in accordance with 

 their true relations in the process of embryological 

 development. 



As both locomotive and nutritive organs are de- 

 veloped from the middle germinal layer, which is 

 derived from a cell outgrowth of the external and in- 

 ternal layers, it does not seem probable that either 

 group of organs is produced by the exclusive influence 

 of one parent. 



Many of the arguments advanced in favor of this 

 theory are drawn from fancied analogies that are not 

 in harmony with well-established facts. 



" It is clear," says Mr. Walker, " that the whole 

 nutritive system, chiefly contained within the trunk, 

 is naturally connected with the senses of taste and 

 smell, which are the guides to the supply of its wants 

 as to food and drink, and therefore the senses con- 

 tained in the face (and consequently the observing 

 faculties dependent on these senses and contained in 

 the forehead) ought to accompany the nutritive system." 



And, by a similar process of reasoning, he con- 

 cludes that " the back-head, containing both the organ 



1 " Outlines of Physiology," p. 954. 



