xxvn 



Therefore, in view of the evidence hitherto obtained, the arguments 

 against the validity of title, to natural consociation, of the Ganoids have to 

 meet the positive evidence of the co-ordinations noted ; the value of such 

 characteristics and co-ordinations can only be affected or destroyed by the 

 demonstration that in all other respects there is (1) very close agreement 

 of certain of the constituents of the subclass with other forms, and (2) 

 inversely proportionate dissimilarity of those forms from any (not all) other 

 of the Ganoids, and consequently evidence ubi plurima nitent against the 

 taxonomic value of the characters employed for distinction. 



And it is true that there is a greater superficial resemblance between the 

 Hyoganoids and ordinary physostome Teleosts than between the former 

 and the other orders of Ganoids, but it is equally true that they agree in 

 other respects than in the brain and heart with the more generalized Ga- 

 noids. They all have, for example, (1) the paraglenal elements undivided 

 (not disintegrated into hypercoracoid, hypocoracoid, and mesocoracoid), (2) 

 a humerus (simple, or divided that is, differentiated into metapterygium 

 and mesopterygium), and (3) those with ossified skeletons agree in the greater 

 number of elements in the lower jaw. Therefore, until these co-ordinates 

 fail, it seems advisable to recognize the Ganoids as constituents of a natural 

 series, and especially on account of the superior taxonomic value of modi- 

 fications of the brain and heart in other classes of Vertebrates, for the same 

 reason, and to keep prominently before the mind the characters in question, 

 it appears also advisable to designate the series, until further discovery, as 

 a subclass. 



But it is quite possible that among some of the generalized Teleosts, at 

 least traces of some of the characters now considered to be peculiar to the 

 Ganoids may be discovered. In anticipation of such possibility, the author 

 had at first discarded the subclass, recognizing the group only as one of 

 the " superorders" of the Teleostomes, but reconsideration convinces him 

 of the propriety of classification representing known facts and legitimate 

 inferences rather than too much anticipation. 



It is remembered that all characters are liable to fail with increasing 

 knowledge, and the distinctness of groups are but little more than the ex- 

 pressions of our want of knowledge of intermediate forms ; it may in truth 

 be said that ability to segregate a class into well-defined groups is in ratio 

 to our ignorance of all the terms. 



SEQUENCE OF GANOIDS. 



The questions, (1) which are the most generalized of the Ganoids, and 

 (2) what is the most natural succession of forms, are not the simple prob- 

 lems they might appear to be, if only the histological condition of the ske- 

 leton should be taken into account. If, on the one hand, in such respects, 



