37 



2nd. It shows us the true position of the Ascidians 

 (Tunicata) in the animal series. If we knew only the 

 adult forms we might regard them as being an aberrant 

 group of the Vermes, or possibly as occupying a position 

 between worms and the lower Mollusca, or we might place 

 them as an independent group ; but we should certainly 

 have to class them as Invertebrate animals. But when 

 we know the whole life-history, and consider it in the 

 light of "recapitulation" and "evolutionary" views, we 

 recognise that the Ascidians are evidently related to the 

 Vertebrata, and were at one time free-swimming Chordata 

 occupying a position somewhere below the lowest Fishes. 



N.B. — In an account of this nature, in which I have 

 obviously made the fullest use of the published works 

 of my predecessors, I have not considered it necessary 

 to burden the text with frequent references to original 

 memoirs. While accepting, then, full responsibility 

 for my statements — nearly all of which I have taken 

 occasion to verify by personal observation— I do not, 

 of course, claim any originality in regard to them. 

 Several excellent bibliographies of the Tunicata have 

 already been published : another seems superfluous. 



