1 62 REESE. 



preserved, after having, with difficulty, been kept alive for six 

 weeks. 



The older larvae which were received, as has been said, in 

 one of the buckets containing eggs, proved to be very hardy, 

 and five or six of them were kept in a 12 1. aquarium for six 

 months or more without the least difficulty. At the end of this 

 time they were killed, two of them having shortly before (Octo- 

 ber 20) transformed into the adult Petromyzon branchialis. 

 During their entire captivity they remained completely buried 

 in the sand in the aquarium. A small stream of water was 

 kept running through the aquarium, though a constant change 

 of water was not necessary. 



In the early part of April, I brought from the herring fisher- 

 ies at Port Deposit, Md., five large sea lampreys (P. marinus) 

 in two tin buckets, each bucket of about 50 1. capacity. Being 

 nearly a meter in length and about 12 cm. in circumference, 

 the five lampreys were rather crowded in the two buckets, and 

 only four of them survived the three-hour journey to the 

 laboratory. They were put into an aquarium (1.5 m. x.Sm. x 

 12 cm.) of running water, where they lived comfortably for sev- 

 eral weeks, until by accident the wire screen was left off the 

 aquarium, and three of them escaped and were found dead upon 

 the floor. On June 22 the remaining lamprey was killed. It 

 proved to be a female, and 250 cc. of ripe ova were " stripped " 

 from her with ease. Had one of the males been kept alive it 

 seems probable that artificial fertilization could easily have been 

 accomplished. 



To sum up, then, it seems (i) that the very small larvae are 

 very delicate and hard to keep in confinement ; (2) that the 

 large larvae are unusually hardy ; and (3) that the adults are 

 able to live in captivity moderately well. 



JOHNS HOPKINS UNIVERSITY. 



