153 
how the epithelial pallium of Cyclostomata and Teleostei be- 
came converted into nervous matter in the forms above them. 
But he was forced to the conclusion (op. cit. p. 119) that ,,wir 
kennen keine Ubergangsglieder zwischen dem rein epithelialen Mantel 
der Knochenfische und demjenigen der Amphibien“ !). 
The fact is, that in no form, high or low, does the ho- 
mologue ofthe epithelial pallium ofthe Ganoid or Te- 
leostean, or, for the matter of that, of the Marsipo- 
branch either, ever at any time become converted 
wholly or partially into nervous matter. 
The statement that the pallium of Ganoidei, Teleostei and 
Marsipobranchii is a degenerate structure is an assumption, un- 
supported by any proof, and opposed to the facts alike of comparative 
anatomy and development. Proof can only be given of its degenerate 
nature, when it be demonstrated, either that it is composed of ner- 
vous matter in the embryo, or that the forms mentioned above were 
descended from animals in which the pallium possessed such a nervous 
structure. I need scarcely say that neither of these conditions has 
been demonstrated. 
Here I would digress a moment in order to discuss briefly a 
very extensive question, viz: — the origin and growth of nerve 
structures. 
There are morphologists to whom the origin of a new organ never 
presents any difficulties worth naming. It first arose in this or that 
group as an entirely new formation, not genetically related to any 
preexisting organ ?). 
The matter is not so simple. A nerve cell cannot be formed 
from any epithelial cell the organism chooses to lay hold of for the 
1) Had this investigator studied Lepidosteus and Protopterus, in- 
stead of Salmo and Triton, he would have used the same words regard- 
ing the transition from Ganoid to Dipnoan. 
2) One hardly believes one’s eyes.when one reads a morphologist’s 
declaration that the segmental nature of the uriuary organs is explained 
by their development as part of the somites. How is their segmental 
nature in Ganoids explained, in which they have no relationships to the 
somites? Are the somites organs, or only the foundations (Anlagen) 
in the embryo of one or more systems of organs? How does RückErr’s 
assumption of the origin of the germinal epithelium from the somites 
bear on the supposed resemblance to the condition of the reproductive organs 
in Amphioxus, until it be demonstrated that those organs arise in Am- 
phioxus also from the somites? Are not the reproductive organs in An- 
nelida also segmental structures? 
