244 REPORT OF THE COMMISSIONERS OF 



Explanation of Illustrations. 



All the illustrations for this article, excepting Nos. 2, 15 and 16, are reproductions of 

 original photographs by the writer. 



Illustration No. 1. — Adult Spawning Male (a) and Female (b) Lake Lampreys, taken from 

 the same spawning nest. The male (a) plainly shows the following characters: The dorsal 

 ridge, the edema or swelling at the anterior end of the base of each dorsal fin, the male organ 

 of intromission, the absence of the anal fin, and at the middle of the tail a sore spot which was 

 made raw by sand coming between the bodies of the pair when they were closely appressed at 

 the instant of spawning. The female (b) shows the shorter but thicker body, distended with 

 eggs, and the anal fin which is distinctly characteristic of the sex. Both show the single median 

 nostril, the seven branchiopores or gill openings on one side, the numerous chitinous teeth, eyes, 

 anal and two dorsal fins, etc. 



Illustration No. 2. — Male and Female Brook Lampreys, on Spawning Bed. (Reproduced 

 from a drawing by Dr. Bashford Dean and Mr. B. F. Sumner, in the "Transactions of the New 

 York Academy of Science," Vol. XVI, Dec. 1897.) The pair at the top of the picture are in 

 mating position, and the one in the lower left-hand corner is trying to move a stone many times 

 its own weight. 



Illustration No. 3. — Head of Lake Lamprey (two thirds of natural size). The neck is twisted, 

 but the gill openings are plainly shown, and one sees the circularly radiate arrangement of the 

 numerous chitinous teeth, and the oral cavity. 



Illustration No. 4. — Mouth of Lake Lamprey (twice natural size). Showing the fimbriae or 

 papillae (at the left) which fringe the outer margin of the oral disk. 



Illustration No. 5. — Head of Brook Lamprey (one and one half times natural size). Showing 

 teeth, eye, gill openings, sense organ, sense papillae, tongue, etc. 



Illustration No. 6.^Head of Brook Lamprey (twice natural size). Showing the fringe of 

 fimbriae all around the mouth; also the numerous sense papillse and the larger sense organ on 

 the neck (the latter on the median line). 



Illustration No. 7. — Head of Brook Lamprey, back view (one and one fourth natural size). 

 Showing the single median nostril, and caudad (toward the tail) from the nostril is shown the 

 pineal body, supposed to represent the rudiment of a third eye. 



Illustration No. 8. — Where the Brook Lampreys Spawn. Looking directly up stream from a 

 point on the bank back of which the water flows. The sticks were set in the spawning beds by 

 the writer purposely to take this picture. Each stake marks a spawning bed. At the extreme 

 right of the picture is the spot where the camera stood in taking No. 9. 



Illustration No. 9. — Where the Brook Lampreys Spawn. Looking across the stream. Each 

 stake marks a spawning bed. At the extreme left of the picture is the spot where the camera 

 stood in taking No. 8. All of the illustrations of this nature here shown were taken in the Inlet 

 of Cayuga Lake, within three miles of Ithaca, N. Y. 



Illustration No. 10. — Where the Lake Lampreys Spawn. Looking diagonally across and up 

 stream. The boy standing in water shows depth across here. Each stake marks a nest, but the 

 stakes without papers mark nests that had been deserted without spawn having been deposited 

 in them. The stream here is twice as wide as in Nos. 8 and 9 ; note that the nests are much 

 further apart than in the preceding. 



