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III. On the Structure and Development of the Shull in Sturgeons (Acipenser ruthenus 
and A. sturio).* 
By William Kitchen Parker, F.R.S, 
Received April 14,—Read May 5, 1881. 
[Plates 12-18.] 
INTRODUCTION. 
Several years ago the late Mr. William Lloyd procured for me from Hamburgh 
seventeen young Sturgeons ( Acipenser sturio ) ; these were from 7 to 8 inches in 
length. Valuable as these specimens were, they were far too much developed for 
embryological purposes; and no pains were spared by me to obtain, if possible, newly- 
hatched embryos and small “fry” of this type. 
More lately it was suggested to me by Mr. Balfour that I should write to 
Professor W. Salensky, of Kasan, who had been working at the development from 
the egg of Acipenser ruthenus, the small Sturgeon or “ Sterlet.”t My application to 
him was promptly and most kindly responded to, and in a short tune I received a 
considerable number of newly-hatched and very small young of that species, ranging 
from 5-| to 14^ millims. in length. Half these were for Mr. Balfour, and the rest for 
me. His researches are embodied in that inestimable work, the second volume of his 
‘ Comparative Embryologymine are here offered to the Society in the accustomed 
form. 
I purposely refrain at present from working out the structure and development of 
the trunk and limbs (I have laboured at these regions, and shall be ready to resume 
that part of my work when this is done); but other workers are from time to time 
taking up those parts, and when once the cephalic skeleton is mastered what remains 
will be a comparatively easy task. 
I am more anxious to be prepared for my own limited work by acquiring a 
thoroughly clear conception of the embryology of each type ; in this my best helper is 
Mr. E. M. Balfour. Professor Huxley is, and always has been, my most valued 
critic and counsellor in all that relates to broad and philosophical views of animal life 
generally, and of the life of the Vertebrata in particular. 
* The skull described in my last paper as that of Discoglossus pictus (Phil. Trans., 1881, Plate 20, 
figs. 7-11, p. 112) was prepared from a badly-preserved, half-grown Dana esculenta. I am indebted for 
this correction, and for a genuine Discoglossus, to M. Boulenger. 
t This species rarely exceeds the length of 3 feet (Gunther, ‘ Study of Fishes,’ p. 361). 
T 2 
