192 BEPORT— 1891. 



which the anterior gangha have become coalescent, the spinal 

 cord having been similarly developed from the ventral chain of 

 ganglia surrounding and coalescing with the wall of the intes- 

 tine, the lumen of which is represented by the central canal. 

 A peculiar tissue which surrounds the brain of the Avmioccetes 

 is supposed to represent the liver of the crustacean. The 

 mouth and oesophagus of the crustacean were represented by 

 the infundibular passage and a posterior median prolongation 

 from the saccus vascuIos7(s. 



It will be observed that these two writers, who have arrived 

 at the same general result in very different ways, are at one 

 on one important point — viz., that the vertebrate nervous 

 system is directly descended from that of the Arthropoda. 



But it is " a far cry " from the arthropod to the vertebrate, 

 and, though I should not like to be called upon to prove that 

 such a descent has not taken place, I doubt if there are many 

 who will admit that the facts brought forward either by Patten 

 or Gaskell can bear the interpretation which they put upon 

 them. 



The great problem of heredity, the problem of the causes 

 and limitations of variation, and that of the influence of external 

 conditions on development seem to be those which at the 

 present time most urgently call for solution. That they will 

 ever all be satisfactorily solved one must be sanguine to hope. 

 The elements and forces concerned in the more subtle pheno- 

 mena of life seem to be quite beyond our possible ken. Much 

 regarding the grosser phenomena has already been explained 

 by approaching them from the chemical and physical stand- 

 point, and it seems only logical to look for further addition to 

 our knowledge to be obtained by the same means. But 

 whether, when we know all that it is possible for us to know, 

 we shall have any real knowledge of the essential nature of 

 that series of properties which constitute vitality may legiti- 

 mately be doubted. 



Much, however, even in this intricate part of our subject 

 doubtless remains to be discovered ; and there are few regions 

 of the domain of biology in which careful and conscientious 

 inquiry, apart from the satisfaction which it brings, will not 

 tend to throw light upon some aspect of these great problems. 



1. Evolution of the Eye. 

 Bv Professor Bickerton. 



