140 PISH HATCHING. 



(Object No. 4.) In tlie sole, also, I remark 

 the same structure. (Object No. 5.) 



Although it may be said that the striated 

 structure of the muscle is no absolute proof of 

 its voluntary nature, I think that, as there is 

 but one instance of involuntary muscle being 

 transversely striated (I allude to the muscles 

 of the heart), we may fairly conclude that 

 the action of the pectoral fin is purely volun- 

 tary. On the other hand, on examining a 

 part of the gill of the young salmon, in 

 which the terminal loopings of the muscle 

 moving it were beautifully shown, I found 

 these muscles (though their fibres were not 

 more than one-third the diameter of those of 

 the pectoral) purely of an involuntary 

 character. 



ISTow^ to turn to the second and still more 



