LINNEA^- SOCIETY OF LONDON. 39 



(2) of the pharyngeal gill-slits, (;5) of the tubular dorsally placed 

 nerve-cord, and (4) of the cerebral eye. The evidence was 

 cumulative, and its value depended on the exact and indisputable 

 nature of the agreements and on the fact that they were found in 

 the two cases compared and in no other animals, so that a common 

 inheritance of these structures by Ascidians and certain Yertebrata, 

 not shared by other forms, was the only rational explanation of 

 the facts. Was tliis the case with the coincidences of structure 

 between the Lamprej' and the Arthropods brought forward by 

 Dr. Gaskell ? Sir Kay Lankester held that the coincidences cited 

 by Dr. Gaskell were not of a sulliciently exact and special nature, 

 nor peculiar to the Vertebrates aud Arthropods, so as to render it 

 necessary to suppose that Vertebrates had been derived from 

 Arthropods, and certainly not of such a nature as to render it 

 reasonable to suppose that the extraordinary conversion of the 

 Artlu'opud's digestive tract into the nerve-tube liad taken place as 

 insisted upon by Dr. Gaskell. 



The view which w"as almost universally accepted at present by 

 zoologists was that when once we pass from the Coelenterate or 

 Entero-coclous grade of animal structure to the Ccelomata or 

 Coelomo-cielous grade, a number of diverging great lines of descent 

 or phyla must be recognised — such as the Echinoderma, the Ap- 

 pendiculata (including Arthropods, Rotifers, and Annelids), the 

 jNIoUusca, the Vertebrata, the Nemertina, and other worm-phyla. 

 As to the beginnings of any of these lines of descent, we had (as was 

 natural enough) very scant indications, nor could we say anything 

 as to the early connection of any one of these great phyla with 

 another. What appeared highly probable, if not certain, was that 

 they all converged to simpler ancestral forms, and that they all 

 inherited the same fundamental tissues, digestive tract aud glands, 

 nephridia, coelom and coolomic ducts, reproductive gonads, blood- 

 vascular system, and nervous cords (many or few), and essentially 

 the same types of sense-organs — ophthalmic, auditory, gustatory, 

 olfactive, and tactile. That the optic vesicles of Arthropoda 

 should agree, not absolutely but in many important respects, with 

 those of Vertebrata, could not be held to indicate special afHnitiea 

 since Annelids, Molluscs, and even Echinoderms had organs of 

 the same kind. Tliat some of the tissues should agree minutely 

 in two of the phyla was not suggestive of special affinity, since 

 many of the tissues agreed in most of the larger phyla. Sir Eay 

 Lankester held and he desired to state it without any offence, 

 that in searching by long and strenuous enquiry for evidence in 

 favour of such a hypothesis as that adopted by Dr. Gaskell, the 

 mind is liable to a kind of " suggestion," and that the psycho- 

 logical condition may become similar to that of those wdio too 

 readily admit all sorts of coincidences as evidence that Bacon 

 wrote the plays of Shakespeare. The heroic nature of the task 

 which it is sought to accomplish undoubtedly in many enterprising 

 and devoted investigators has re-acted unfavourably on the 



