of the Dichotomous System. 203 



diately between the cow and the hawk, he took himself a leap 

 as frolicsome as Dr. Fleming has since taken in placing the 

 Tunicata between the Mollusca and Annulosa, as the link of 

 their immediate connection. 



Such being the unequal nature of chasms, and their exist- 

 ence being necessary to form that of a continuous chain of 

 animals, the question now to ask is not whether the transition 

 from Vertebrata to the Invertebrata of Lamarck be impercepti- 

 bly gradual (for that, although theoretically supposable, has 

 been shown in nature to be impossible), but whether any ani- 

 mals of the Mollusca approach more than the others to the 

 structure of the Vertebrata, and any of the Vertebrata more 

 than the others to that of the Annulosa. I have already de- 

 cided this last question, and proved a number of relations of 

 affinity between Mollusca and Vertebrata, and between Verte- 

 brata and Annulosa, which cannot, as the Doctor imagines, 

 be relations of analogy, for they want the great characteristic 

 of these last, namely, their parallelism. If any relations exist 

 between Cephalopoda and Chelonial reptiles, they cannot be 

 relations of analogy, and therefore must be relations of affinity. 

 Dr. Fleming indeed gives, as usual, a garbled quotation from 

 a passage that I have cited at length from M. Cuvier, but I 

 will not repeat here what I have sufficiently proved. So far 

 as the mere name goes, the genus Chelys is cephalopod as 

 well as Loligo. I trust that he will endeavour to become 

 acquainted with these and other genera of the two groups, 

 and that he will compare Messrs. Guthrie's and Holberton's 

 late anatomy of tortoises with that of Cephalopoda by M. Cu- 

 vier, or, still better, that he will at length take the scalpel in 

 hand. The genera just mentioned are not indeed the nearest 

 to each other of their respective groups, but enough and more 

 than enough is evident to prove their approximation. If any 

 relations exist between them, as there is no parallelism they 

 cannot be relations of analogy ; or even could Dr. F. reduce 

 the numerous relations I have pointed out (Horce Entom. 

 p. 248—261) to parallelism, and thus show them to be rela- 

 tions of analogy, it would only add to our conviction that the 

 two groups are contiguous, for such parallelism characterizes 

 two contiguous circles. So, let Dr. Fleming dichotomize until 

 doomsday, — unless indeed he denies the truth of the anatomical 

 facts I have detailed on this question, — the goal he will infallibly 

 arrive at will be the same, namely that Vertebrata are connected 

 with the Mollusca by means of the Cephalopoda and Chelonian 

 reptiles. But " has the attempt to unite the Vertebrata with 

 the Annulosa been more successful ? " No, not more so ; but 

 quite as successful. 



2 D 2 Our 



