96 JEAN DAWSON. 



breeding season and one specimen caught in December. The 

 lampreys caught in the breeding season showed the same atro- 

 phied condition of the intestine that had been found in our own 

 material, but the intestine of the one that was caught out of the 

 breeding season was found to be gorged with food. The intes- 

 tine measured 4 cm. in circumference while the intestine of a 

 specimen of the same size caught in the breeding season measured 

 but 6 mm. The resophagus was entirely empty. Among the 

 contents of the intestine solid particles could easily be seen with 

 the unaided eye, while a microscopic investigation proved most of 

 these to be muscular tissue. The more liquid parts were past 

 recognition. There were recognizable bits of striated muscle 

 about 1 2 mm. long, a gill and a rib of a small teleost fish. The gill 

 was i cm. long and bore filaments 5 mm. in length ; the rib was 

 2. cm. long. It is impossible to tell whether the lamprey came 

 by this small fish directly or from the intestine of a larger fish 

 which served as its prey. 



In any case it appears that the attached P. inarinus nnicolor 

 may feed not only on blood but on more solid tissue. The very 

 extensive injuries produced by this species and figured by Surface 

 (1893) are in accord with this conclusion. Presumably P. 

 inarinus and Ichthyomyzon have similar habits. According to 

 Gage (1893) the adult Lampetra unldcri takes no food. 



III. MECHANISM OF RESPIRATION. 



A. WJieii the Lamprey is Attaclied. Respiration may readily 

 be studied when the lamprey is attached, and has been described 

 by Bert (1867), Gage (1893) and Meyer (1835). The respiratory 

 currents may be easily seen in L. wilderi and in Ichthyomyzon 

 concolor by means of particles suspended in the water. There is 

 a rapidly alternating contraction and expansion of the branchial 

 region. At each contraction a current of water leaves all the 

 external branchiopores simultaneously and passes outward and 

 backward at an angle of 45 with the long axis of the body. 

 At the same time a current issues from the nostril. With the 

 expansion of the branchial region the water is seen entering the 

 external branchiopores in lines converging from all directions to 

 each aperture and at the same time a similar current enters the 

 nasal opening. 



