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X. On the Skeleton of the Marsipobranch Fishes .—Part IT. Petromyzon. 
By William Kitchen Parker, F.R.S. 
Received January 10,—Read January 18, 1883. 
[Plates 8, 10, 14, 15, and 18-26.] 
In this Second Part the Marsipobranch type of skeleton will be described in several 
stages, as far as my materials go ; afterwards, I hope to be able to show in a Third 
Part some of the organs in the act of transformation, the specimens for which I am 
now expecting. 
In the present paper I shall describe :— 
A. The skeleton after transformation. 
a. In the adult Petromyzon Jluviatilis. 
b. In one-third grown P. marinus. 
c. In newly metamorphosed P. marinus. 
d. In very small (not quite transformed) young of P. marinus. 
B. The early embryo of P. planeri; and 
C. The larval form (or Ammoccete ) of P. Jluviatilis, ready for transformation.* 
These stages give most of the facts we are looking for, but it will be a satisfaction 
to be able to explain every step in this remarkable metamorphosis.! 
The friends to whom I am indebted for materials for the present paper are 
Professor Huxley, F.R.S., Francis Day, Esq., F.L.S., the late Frank Buckland, 
Esq., Professor Ray Lankester, F.R.S., the late Professor F. M. Balfour, F.R.S. 
(in conjunction with Osbert Salyin, Esq., F.R.S.), F. G. Penrose, Esq., and Dr 
Albert Gunther, F.R.S. 
* Since this paper was read I have received figures of the early embryo of Callorhynchus from my 
son, Prof. T. J. Parker, who has succeeded in finding an early stage of this important type on the 
shores of New Zealand. I am now satisfied that the Chimseroids are not nearly related to the 
Petromyzoids. 
t The Bibliography has been given in the First Part. 
