151 
the consideration of the comparative morphology and development of 
the urinogenital organs, and of the fore-brain. In conclusion it shall 
be shown how these and other facts justify the arrangement of the 
sub-classes of the Ichthyopsida !) which now follows. 
The epitheliai nature?) of the pallium in the fore-brain, the total 
degeneration of the pronephros in the adult, and its non-conversion 
in any part into an efferent duct for the female sexual products, i. e. 
the absence ofa Müllerian duct, sharply define the Marsipobranchii, 
the Ganoidei and Teleostei on the one hand from the Selachii 
and Dipnoi on the other; for in the two latter sub-classes the fore- 
brain roof is mainly nervous, and a portion of the pronephros persists 
as the funnel of the Müllerian duct. 
The further subdivisions of these two groups are the existing five 
families above mentioned. I shall, however, give reasons presently 
for regarding the Marsipobranchii as close allies of the Ga- 
noidei, and I fully agree with those morphologists who place the 
Teleostei very near the Ganoidei. 
The Dipnoi may be looked upon as very low Amphibians, as 
descendents of that group of fishes from which the Amphibians were 
derived. Whether Amphibians arose from forms which possessed 
limbs like those of Ceratodus or Protopterus is a point on which I 
have no opinion to offer. 
The morphology of the pallial region of the fore-brain. 
The controversies as to the nature of the fore-brain region of 
fishes, especially of Teleostei, are well-known, and I deem an ac- 
count of them here unnecessary. 
A new light was thrown on the question when RABL-RÜCKHARD *) 
1) In a addition to the characteristics of the Ichthyopsida as 
given by Huxıer (Anatomy of the Vertebrated Animals, p. 100 — 101) 
the additional one, of the highest importance, is the presence of functional 
lateral sense organs on the surface of the body during the whole, 
or in Anurous Amphibia, a part of the free life. This character distin- 
guishes them completely from the Sauropsida and Mammalia in which the 
lateral sense organs are partly only embryonic rudiments and partly per- 
haps converted into organs of taste, i. e. not on the surface of the body. 
2) By this I mean the absence of nervous matter in the roof of the 
fore-brain. 
3) See the account of his views in Biol. Centralbl. Bd. IV, p. 499 
bis 510. In this paper and in Epınser’s excellent „Untersuchungen über 
