ON THE OUTLOOK OF VERTEBRATE MORPHOLOGY. 83 



The author promises a third part of his monograph, to 

 be devoted to a consideration of the soft parts, upon which 

 Max Weber 57 and Turner 58 have recently thrown so 

 much light, together with a final discussion of the position 

 of the cetacea in the animal series. Meanwhile, he has 

 earned the lasting gratitude of all, in having simplified 

 our conceptions of the structural peculiarities of these 

 remarkable creatures, and brought them into much closer 

 harmony with the more normal placentalia. 



The dipnoan fishes, to a consideration of the early 

 stages in development of one of which the second of the 

 two monographs specially under review contributes a 

 first instalment, are represented by three living genera of 

 fresh-water fishes — Ceratodus in Queensland, Protopterus 

 in Tropical Africa, and Lcpidosiren in the Amazons — and 

 all doubt as to the supposed non-validity of the last- 

 named genus is dispelled, by the authoritative record of 

 six known examples preserved in the European mu- 

 seums. 59 The classical monographs of Hyrtl,'"' Giinther 01 

 and Huxley 62 upon the gross structure of these creatures, 

 and the supplemental ones of Gegenbaur, 63 Wiedersheim, 64 

 Parker 65 and others, need no comment here, except that, 

 in having proved these fishes to differ from all others in 

 proportion as they suggest the amphibian type of organi- 

 sation, they bring us in touch with an approximate 

 realisation of the characters demanded of those creatures 

 transitional between the aquatic and terrestrial vertebrata 

 — a topic of obviously supreme interest and importance. 



Huxley has defined Ceratodus m as a "wonderful 

 creature contrived for the illustration of the doctrine of 

 evolution". It cannot, however, be denied that the 

 experimental and morphological inquiries into the acces 

 sory organs of respiration occurring among the Tropical 

 Teleosteans, 67 and those of Johannes Miiller 68 and Ramsay 

 Wright 69 concerning the behaviour of the pneumatoccele 

 and aortic arches in Poly terns and Amia, justify hesitation, 

 in accepting the customary belief in an intimate genetic 

 relationship between the Dipnoi and Amphibia. The 



