re 
Nachdruck verboten. 
The inter-relationships of the Ichthyopsida. 
A contribution to the morphology of Vertebrates. 
By J. Brarp, Marine Station, Dunbar, Scotland. 
(Schluß.) 
The lung and swim-bladder. 
As mentioned in the introduction it is the fashion to accept the 
homology of lungs and swim-bladder. If the thesis be true that the 
Dipnoi and Amphibia never had a Ganoid ancestry, — and to 
my mind there cannot be a particle of doubt about the matter — the 
basis of this supposed homology is lost. 
I have no hesitation in maintaining that neither Selachii nor Di- 
pnoi arose from fishes which possessed a swim-bladder. As a matter 
of fact, however, the onus of proof that they did rests with the oppo- 
site side. 
Miıktucno-MAcLaAY’s?) statements as to the existence of a rudi- 
ment of a swim-bladder in advanced embryos of certain sharks, 
Acanthias, Mustelus, etc. are incorrect, for the existence of such a 
structure in those two forms is a myth. My thesis is that only those 
fishes, e. g. Marsipobranchii, Ganoidei and Teleostei, 
which are out of the line of ancestry of the remaining Vertebrates 
every possessed a swim-bladder. 
1) Jenaische Zeitschr. f. Naturwiss. 1868. I am not sure of the 
exact date. 
2) On the grounds of what I may call topographical comparative 
anatomy ALBRECHT has already denied the assumed homology. — See his 
paper ‚Sur la non -homologie des poumons des Vertébrés pulmonés avec 
la vessie natatoire des Poissons. Bruxelles 1886. 
12* 
