loo JoiRNAL or Comparative Nei^rology. 



belief that consciousness is a necessary condition to such re- 

 actions. Inasmuch as these motions are called out by irrita- 

 tions of various spots within the visual (sensory) area having 

 no direct relation to the eye-muscle centre " F,'' as deter- 

 mined by Fritsch and Hitzig, and since the resulting motions 

 are correlated just as they would be if the animal were con- 

 sciously fixing the gaze upon a special point, and, finally, 

 because these phenomena can only be prevented by division 

 of the fibres of the corona radiata, Obregia concludes that 

 such irritation actually produces optic sensations. 



It is generally admitted that an irritation of a spot upon 

 the retina produces in consciousness the image of an external 

 luminous point in the diagonally opposite part of the field of 

 vision. The experiments show that irritation of the 

 posterior part of the visual area produces an upward 

 motion of the eye-ball, an irritation of the anterior part, 

 a motion in the downward direction, or, in other words, just 

 the same motion as would be called out by the irritation of 

 the lower or upper retinal areas respectively. The irritation 

 of the centre of most distinct vision produces simply the 

 appearance of attentive gazing with slight motion. 



Without following these experiments in full, it may be 

 said that, if proven accurate, they seem to verify the most 

 detailed ascertions of Munk and prove a direct connection 

 between the sensory and motor areas. 



There can be no doubt that the theoretical problem of 

 morphology, which has excited most interest of late and 

 which seems to have the strongest hold on the imagination of 

 investigators generally, is the question as to the origin of the 

 head and its various correlated structures. One reason for 

 this prolonged and persistent eftbrt to solve a problem which 

 is essentially simply a theoretical one lies in the fact, that the 

 formation of the head is the culmination of the whole series 

 of progressive changes which constitutes organic evolution. 

 Whatever view may be taken of " cephalization " in its 

 technical form, all must agree that the tendency of evolution 



