Vol. IX. 



BIOLOGICAL BULLETIN 



THE BREATHING AND FEEDING MECHANISM OF 



THE LAMPREYS. 1 



JEAN DAWSON. 



CONTENTS. 



PAGE. 



I. STRUCTURES INVOLVED IN BREATHING AND FEEDING 2 



A. Oral Funnel, Mouth Cavity and Tongue 2 



B. Pharynx 6 



C. Gills 12 



D. Nasal Sac 20 



The present study of the respiratory mechanism of the lampreys 

 was undertaken at the suggestion of Professor. Jacob Reighard 

 and has been carried out under his direction. ' Prese'Wed material 

 of Pctromyzon inarinus Linnaeus, Petrowiyzon marimis nnicolor 

 (De Kay) and Lampctra ivildcri Gage has been examined, but 

 these three species have been found to be so nearly alike in the 

 structure of their respiratory mechanism that the following 

 anatomical description of Petromyzon marinns holds good in all 

 essentials for the other two species. Where measurements are 

 given they are taken from P. marinns and refer to individuals of 

 average size. The close relation between feeding and breathing 

 in the lamprey has made it necessary to consider the mechanisms 

 of the two together. There is without doubt a similar close rela- 

 tion between the mechanism of respiration and that of circulation 

 but this has not been included in the scope of the present paper. 



I. STRUCTURES INVOLVED IN BREATHING AND FEEDING. 



Food entering the funnel-shaped cavity of the oral hood 

 passes thence at the apex of the oral hood into the mouth cavity 



1 Contributions from the Zoological Laboratory of the University of Michigan, No. 92. 



I 



