42 COMPARATIVE PHYSIOLOGY OF THE BRAIN 



that forms which are morphologically alike need not 

 necessarily be alike in all their reactions. Experiments 

 on fermentation show that a small stereochemical dif- 

 ference of a carbohydrate or proteid can produce an 

 entirely different physiological effect. 



The possibility, of course, remains that scattered 

 ganglion-cells exist in Ascidians under the epidermis 

 just as in Medusae. Mr. Hunter, who has studied the 

 nervous system of Ascidians, informs us that he has 

 found cells in certain places under the epidermis of As- 

 cidians which he believes to be ganglion-cells. But 

 after all that has been said about the scattered gan- 

 glion-cells in Hydromedusae (see page 19) and their 

 role in rhythmical contractions, it is not necessary to 

 consider the importance of scattered ganglion-cells for 

 reflexes. Schaper has recently made an observation 

 which makes it seem as though in the young larvae of 

 Amphibians conditions similar to those in Ascidians 

 exist. He amputated the brain of the larva of a frog 

 during the first days of development, and saw that the 

 animal was still able to move spontaneously seven days 

 after the operation. When sections of the animal were 

 made, it was found that the spinal cord had also per- 

 ished (2). This observation should be repeated and 

 enlarged upon. It is quite possible that during the 

 first days of development a direct transmission of the 

 waves of stimulation may take place from the skin to 

 the muscles in the larva of the frog, without the in- 

 tervention of the central nervous system, as happens 

 in the Ascidians. 



