170 JOHN BEARD 



THE SYSTEM OF BRANCHIAL SENSE ORGANS AND 

 THEIR ASSOCIATED GANGLIA IN ICHTHYOPSIDA. A 

 CONTRIBUTION TO THE ANCESTRAL HISTORY OF 

 VERTEBRATES. 



By John Beard, Ph.D., B.Sc, Berkeley Fellow of Owens College, Victoria 

 University, Manchester. 



[Plates VII, VIII, & IX.] 



Introduction. 



Among the many weighty questions which have arisen with the rise 

 and progress of comparative embryology, that of the origin and an- 

 cestral history of Vertebrates has occupied, and still occupies, an 

 important place. 



That the question, if capable of solution at all, would be solved by 

 the discoveries of embryology, is now, and has been for the last ten 

 years, a general opinion among zoologists. So much for a general 

 ao-reement. But as to the particular line of descent one might recall 

 half a dozen different theories supported by different' schools of workers. 



The impulse to these speculations was first given by the discovery 

 of the tadpole-like larva of Ascidians, and the opinion that Vertebrates 

 were derived from Ascidians we owe to Kowalewski and Kupffer. This 

 view has had its day, and is now only a reminiscence. 



Another important theory, important because clothed with the 

 authority attached to the name of Balfour, is the theory that Verte- 



