NOTES. 



5. (p. 22.) HUXLEY had recognised in 1874, in the light of 

 Kowalevsky's work, that the atrial cavity of Amphioxus was lined 

 by an epithelial layer derived from the ectoderm, but came to the 

 conclusion that it was, by the very fact of its inversion within the 

 body, converted into peritoneal epithelium. He applied the same 

 interpretation to the opercular chamber of the Amphibian tadpole, 

 and gave to a body-cavity of this character the general name of 

 epicene. ROLPH'S merit consisted in distinguishing clearly between 

 atrial epithelium and peritoneal epithelium, and hence between 

 atrial cavity and true body-cavity. 



6. (p. 38.) There is a great deal of difference of opinion as to 

 the exact nature of that dense refringent tissue which forms the 

 outer layer of the cutis and the skeletal rods of the gill-bars. 

 LANKESTER regarded them both as the products of connective 

 tissue-cells, hence belonging to the mesoderm, while HATSCHEK 

 and SPENGEL looked upon the outer layer of the cutis as the 

 product of the ectoderm, of the nature of a basement membrane. 

 SPENGEL again has advocated the view that the skeletal rods of the 



