io The Ganoids 



" It has been objected that the Ganoids do not constitute 

 a natural group, and that the characters (i.e., chiasma of optic 

 nerves and multivalvular bulbus arteriosus) alleged by Miiller 

 to be peculiar to the teleostomous forms combined therein are 

 problematical, and only inferentially supposed to be common 

 to the extinct Ganoids so called, and, finally, such objections 

 couched in too strong language have culminated in the assertion 

 that the characters in question are actually shared by other 

 physostome fishes. 



" No demonstration, however, has been presented as yet 

 that any physostome fishes do really have the optic chiasma 

 and multivalvular bulbus arteriosus, and the statement to the 

 contrary seems to have been the result of a venial misappre- 

 hension of Prof. Kner's statements, or the offspring of impressions 

 left on the memory by his assertions, in forgetfulness of his 

 exact words. 



" But Prof. Kner, in respect to the anatomical characters 

 referred to, merely objects: (i) that they are problematical, 

 are not confirmable for the extinct types, and were probably 

 not existent in certain forms that have been referred to the 

 Ganoids; (2) the difference in number of the valves of the 

 bulbus arteriosus among recent Ganoids is so great as to show 

 the unreliability of the character ; (3) a spiral valve is developed 

 in the intestine of several osseous fishes (' genera of the so-called 

 intermediate clupeoid groups'), as well as in Ganoids; and 

 (4) the chiasma of the optic nerves in no wise furnishes a posi- 

 tive character for the Ganoids. 



" It will be noticed that all these objections (save in the 

 case of the intestinal spiral valve) are hypothetical and vague. 

 The failure of the intestinal spiral valve, as a diagnostic char- 

 acter, has long been conceded, and in this case only have the 

 forms that prove the failure been referred to ; in the other cases, 

 where it would be especially desirable to have indicated the 

 actual types falsifying the universality or exclusiveness of 

 the characters, they have not been referred to, and the objec- 

 tions must be met as if they were not known to exist. 



" (i) The characters in question are, in the sense used, 

 problematical, inasmuch as no examination can be made of 

 the soft parts of extinct forms, but with equal force may it be 



