EXPERIMENTS ON ASCIDIANS 39 



centres " of higher animals. It is frequently stated 

 that in higher animals the ganglia have assumed func- 

 tions which in lower animals can be performed by the 

 peripheral organs. It is similarly stated that the higher 

 the animal ranks in the natural system, the more the 

 functions "migrate" toward the cerebral hemispheres. 

 But how such an upward migration of functions is 

 conceivable, none of these authors attempt to explain. 

 It can easily be shown, however, that conditions are 

 the same in higher and lower animals. We must only 

 be careful to homologise a lower form with a single 

 organ or segment of a higher animal. When the in- 

 tensity of the light is suddenly increased, the pupil of 

 our eye becomes narrower. The sphincter of the iris 

 contracts, and the rays of light are excluded just as 

 foreign bodies are shut out by the contraction of the 

 sphincters in the Ascidians. In the eye, just as in the 

 Ascidian, we have to deal with a typical reflex act. 

 The increased intensity of the light stimulates the 

 retina. The stimulation passes through the optic 

 nerve to its centres, and is carried from there by 

 means of the oculomotorius nerve to the sphincter of 

 the iris, which contracts. It would nevertheless be 

 wrong to assume that the centre for the pupillary 

 reflex plays any other part in this process than that of 

 a protoplasmic connection between the retina and the 

 iris. It has been shown by Arnold, and later by 

 Brown-Sequard and Budge, that even in the excised 

 iris the pupil still contracts when the light strikes the 

 former. I myself have often observed in sharks, 



