142 



Mr. W. K. Parker. 



[May 5, 



II. " On the Structure and Development of the Skull in Stur- 

 geons (Acipenser ruthenus and A. sturio)" By W. K. 

 Parker, F.R.S. .Received April 14, 1881. 



(Abstract.) 



Since the publication of my paper on the sknll of the salmon, a 

 Teleostean fish, I have made many efforts to obtain early stages of the 

 Ganoid types. Until the last two years, however, I have failed. At 

 last, I have been taken almost by surprise by the kindness of Professor 

 W. Salensky, of Kasan, and of Professor Alexander Agassiz, of 

 Harvard College, Cambridge, Mass. The former has supplied Mr. 

 P. M. Balfour and myself with a number of bottles of early stages of 

 the sterlet {Acipenser ruthenus), whilst from Professor Agassiz we 

 have received fifty-four bottles of fecundated eggs and embryos of 

 various stages of the Lepidosteus. 



Mr. Balfour's researches on the early stages of the sterlet, supplement- 

 ing those of Professor Salensky, will appear immediately in the second 

 volume of his work on " Comparative Embryology," and the result of 

 his researches on the development of the Lepidosteus, in which he was 

 assisted by one of my sons, will be sent to the Royal Society towards 

 the fall of the present year. That paper, now far advanced, will 

 be accompanied by one, already written and ready for publication, by 

 me, on the development of the skull in the same species of Ganoid 

 fish. 



I had long ago received from the late Mr. Win. Lloyd a number of 

 young sturgeons of the common kind, but the smallest of them was 

 7 inches long ; the largest of the larvaa of the small Russian species 

 was only seven-twelfths of an inch in length. 



Yet, notwithstanding the small size of these larvae, their develop- 

 ment had advanced very greatly and the cartilaginous framework was 

 in a state of incipient completeness. Any little difficulty felt on step- 

 ping from the structure of specimens seven lines long to those seven 

 inches long was done away with by the means at hand of comparison 

 of the two types of Ganoids, namely Acipenser and Lepidosteus ; for of 

 the latter my specimens were very numerous and in every desirable 

 stage. 



Of the fry which Professor A. Agassiz and his talented assistant, 

 Mr. S. Garman, had succeeded in rearing, many had reached to the 

 length of an inch, and were pretty exact miniatures of their parents. 

 But, besides these, I have received from Professor Burt Wilder, of 

 Cornell University, Ithaca, Mass., U.S., some specimens of Lepidosteus 

 ranging from 1 to 4-J inches in length. 



