310 PROCEEDINGS OF THE ACADEMY OF [1884, 



In Branchiostoma lanceolatum we find the degeneration has 

 reached its greatest extreme. There exists no trace of the eye, 

 in form, and we recognize its existence only by a slight deposit 

 of pigment on the anterior end of the neural canal. The brain 

 itself has disappeared in this degenerate form, it going hand in 

 hand with the eye, so that the only remnant of it is a spot of 

 pigment on the anterior end of the neural canal. 



Now this deposit of pigment that we find in Branchiostoma — 

 and a similar deposit in the nerve-centres of some of the larvae 

 of the Ascidia, looked upon at one time as the ancestors of the 

 Yertebrata, while they are if Vertebrata at all, greatly degenerated 

 ones — led Lankester ' to regard the primitive type of the Verte- 

 brata as a transparent animal with eyes sessile on the brain, 

 I am of the opinion that forms so degenerate as Branchiostoma 

 and the Ascidia should not be taken as a standard, on which to 

 base our conclusions for the origin of the Vertebrata. 



In conclusion I may quote a passage from Tyndall,^ which we 

 have taken for our motto : " The eye has grown for ages toward 

 perfection, but ages of perfecting' may still be before it." 



* Lankester, E. R., Degeneration, a Chapter in Darwinism. Nature 

 series. London, 1880. 



' Tyndall, Jolin, Six Lectures on Light, London, 1873. 



