RELATIONS AND PHYLOGENY OF THE TUNICATA. 



It incay reasonably be expected that at the cud of a Report upon sucli an extensive 

 eoUection as the Challenger one, containing representatives of all groups (;f the 

 Tunicata, I should state the conclusions at which I have arrived in regard to the 

 relations of the Tunicata to one another, and to other groups of animals. Such con- 

 clusions are of necessity speculative in their nature, and may therefore be regarded as 

 (piite distinct from the preceding systematic and anatomical parts of the work. 



I am aware that by some naturalists speculations as to the affinities and phylogeny 

 of animals are still regarded as worthless and even dangerous ; but probably such views 

 will become rarer year by year as biology, by means of theories and reasoning, becomes 

 more and more a true science and less of a mere accumulation of facts. I regard 

 phylogenetic conclusions founded upon the structure and development of the animals 

 as not only most valuable and interesting in themselves, but as exercising an important 

 influence upon the further progress of the science. And I consider that it is the duty 

 of a biologist, who has made a special study of a group of animals or plants, to attempt 

 to express any views he has formed as to their relations in a phylogenetic form. Such 

 theoretical inductions from his observations are most suggestive and helpful to other 

 workers. If his conclusions be correct, they form an important contribution to know- 

 ledge; and if they be incorrect, they may still be useful in directing attention to 

 points requiring further investigation, and at any rate the errors will soon l)c discovered 

 and corrected by his successors. 



It is only fair to those who may read my conclusions as to the relations of tho 

 Tunicata that I should state what opportunities I have had of studying the group. 

 I have now been occupied continuously for nearly ten years in investigating Tunicata, 

 including, besides the large and varied Challenger collection, the specimens in the 

 British Museum, the collections sent out by the Naples Zoological Station, and by the 

 United States Commission of Fish and Fisheries, the collections in a number of museums 

 at home and abroad, and finally, a large number of the British and French Tunicata in 

 a living condition. Altogether I have been enabled to dissect for myself and examine 

 microscopically specimens of nearly every genus in the group — including all the 



(ZOOL. CHALL. EXP. — PART LX.XVI. — 1888.) Gggg ^^ 



