510 Dr KNOX on the Natural History of 



EXPLANATION OF PLATE XI. 



FIG. I. Food of the clean Salmon. The Asterias glacialis, or Cross-fish, here re- 

 presented, is the most common of its kind. The dorsal integumentary surface 

 has been cut away, together with all the internal soft organs, except the ova, 

 and consequently the view given is that of the skeleton of the internal abdo- 

 minal surface. The animal has uniformly five rays,_one of which only is fully 

 represented. The ova (c), inclosed by an extremely delicate oviduct, have 

 been drawn out, in order to display their appearance more completely. In 

 the living animal, they occupy the grooves on each side the mesial line of each 

 ray, and are of course entirely concealed until a section is made. 



a, The finished ray. 



b, The central opening of the animal. 



c, The ova, which, in the recent state, when fully developed, are of a rich cream 



colour. They form (with the eggs of other Actinodermata and Crustacea) 



the food of the salmon. 



Note. In these animals, the ova, during their progress to complete de- 

 velopment, pass through a great variety of colours, but, when fully formed^ 

 assume invariably the distinguishing shade observed in the adult animal. 

 In the Kelt, for instance, a species having thirteen rays, the ova are of a 

 bright clear vermilion. 



Fio. II. Food of the Herring, taken off the Isle of May during the month of De- 

 cember ] 832. 



A, Natural size of the adult full-grown animal. 



B, Magnified view of the most perfect specimen which could be found. 



C, Magnified view of a detached spine, being appendages of the legs and feelers 

 of the adult animal : they, together with the testaceous cases covering the 

 body of the animal, form the brownish layer found in the stomach of the clean 

 herring, as mentioned in the text. Thousands of them were raised on the 

 point of a delicate silver probe. 



FIG. III. Food of the Vendace, taken in the Castle Loch of Lochmaben 18th Sep- 

 tember 1832. 



A, Natural size of the animal. 



B, A side view magnified. 



a, The antennae or feelers. 



b, The eye. 



