428 



Regia Fredericiana, die 26 Januarii 1838 celebrandum indicit 



Collegium Academicum. 4to. — From the University. 

 Dr Lorenz Hiibner's Biographische Charakteristik. Von Joseph 



Wiskmayr. 4to. — From the Royal Academy, Munich. 

 Ueber die Gliederung der Bevolkerung des Konigreichs Bayern. 



Von Fr. B. W. Von Hermann. 4to. — From the same. 

 Maps of the Geological Survey of India. — From the Hon. East 



India Company. 



Monday, 16th Decerribei' 1856. 



Professor CHRISTISON, V.P., in the Chair. 



The following Communications were read : — 



1. On the Ovum and Young Fish of the Salmonidse. By 

 William Ayrton, Esq. Communicated by Professor All- 

 man. 



The paper contained a series of observations on the development 

 of the embryo in the salmon, made on ova procured from an esta- 

 blishment for the artificial propagation of this fish, at Overton, 

 on the river Dee. The author's observations commenced about the 

 37th day after impregnation, and were continued from that period to 

 the time when the vitellus becomes finally absorbed. The progressive 

 development of the various organs was described, and the principal 

 steps illustrated by carefully drawn and expressive figures. With 

 regard to the proper time for transit, the author arrived at some 

 practical conclusions. lie maintained that the ova, after impregna- 

 tion, should be as little disturbed as possible for the first thirty or 

 thirty-five days, but he proved that at the end of that period they 

 may be exposed to great changes of temperature, and of other 

 external conditions, with comparative impunity ; and he was of opi- 

 nion that they would then endure a transit of some days if only sup- 

 plied with moisture by means of moss, wool, or similar material. 

 He further concluded, as the result of various observations and ex- 

 periments, that if the transit be not made when the ovum is from 

 thirty to forty days old, it will be made with most safety after the 

 young fish has attained an age at which the yelk is wholly or nearly 

 absorbed. 



