748 ^^ J BEARD, 



Ganoids 0, but are far more related to the latter than to the former. 

 Not that they are descended from either group ; in all probability they 

 are a degenerate offshoot of the gnathostomatous ancestors of the two 

 groups. 



In the number of gill clefts, and the presence of a subintestinal 

 vein, they stand nearer to the Selachians than to the Ganoids, while 

 in the great development of the oral and neural hypophysis, the con- 

 dition of the urino-genital organs , and the great modification of the 

 mouth parts they find allies among the Ganoids, with which group 

 they agree in their migration wholly or partially to the rivers and 

 fresh-water streams. 



And finally, in the segmentally arranged slime or mucous sacs of 

 the Myxinoids, the high development of the parietal eye in Petromyson, 

 and the persistence of the hypophysial-gut passage in the Myxinoids 

 they are far more primitive than any existing Ganoid or Selachian. 

 And there seems to be no reason for supposing that the group is a 

 degenerate offspring of either Selachians, or Teleosteans. 



And thus one can say with Balfour that the Marsipobranch 

 fishes are the remnants of a very primitive group, nay more, that 

 they are the most primitive of existing Vertebrates. But his view 

 of their prae-gnathostomatous nature must be rejected, and certainly 

 Balfour himself would now have relinquished it. 



One word more from Prof. Dohrn and I have done. He says : — 

 „Die Trennung, welche die bisherige Morphologie zwischen eigentlichen 

 Fischen und Petromyzonten glaubte annehmen zu müssen, beruht auf 

 irrthümlicher Interpretation von Verhältnissen, welche in ihrem Zu- 

 standekommen nur begriffen werden müssen, um sofort die viel grössere 

 und nähere Zusammengehörigkeit der beiden Gruppen erkennen zu 

 lassen" (5, p. 52). 



I desire to express here my best thanks to Profs. Wiedersheim 

 and Howes for their good counsel; and to Dr. Günther's and Prof. 

 Howes' kindness I am, moreover, indebted for some of the rare material 

 used in this small research. 



1) The relationship of the Marsipobranchii to the Ganoidei will 

 be treated of in a future memoir on Ganoid morphology. 



