ANTERIOR LIMBS OF BIRDS, ETC. 91 



Mr. Owen has remarked that, " when the lam- 

 prey is firmly attached, as is commonly the 

 case, to foreign bodies, by means of its suc- 

 torial mouth, it is obvious that no water can 

 pass by that aperture from the pharynx to the 

 gills ; it is, therefore, alternately received and 

 expelled by the external apertures, (the gill- 

 orifices along the neck.) If a lamprey, while 

 so attached to the side of a vessel, be held with 

 one series of apertures out of the water, the 

 respiratory currents are seen to enter by the 

 submerged orifices, and after traversing the 

 corresponding sacs and the pharynx to pass 

 through the opposite branchiae, and to be forc^ 

 bly ejected therefrom by the exposed orifices. 

 The same mode of respiration must take place 

 in the myxine, while its head is buried in the 

 flesh of its prey." — Yarrell. 



The sea-lamprey ascends rivers to breed, 

 and produces pits and furrows in the bed to 

 receive the eggs, by removing the stones with 

 its suctorial mouth. The power of this fish is 

 very great, and stones of a large size are easily 

 transported, the furrow being rapidly formed. 



Thus far, then, have we cursorily traced the 

 modifications of the anterior limbs, (glancing 

 occasionally at the hinder extremities also,) 



