The Lake and Brook Lampreys of Nezv York 491 



Fig, 36. (X 6). Transection of a female brook lamprey, about 190 

 millin'ieters in length. Just transformed ; caught in Octolier. For com- 

 parison with the male (Fig. 35), and with the female lake lamprey at 

 the same stage (Fig. 34). It will be seen that the brook lamprey's 

 ovary is much nearer maturity than is that of the just transformed lake 

 lamprey. 



Fig. 36 A. (X 53). Ovum from the ovary of the same specimen as 

 figure 36. To show the size of the ovum in the just transformed brook 

 lamprev, aud for comparison with the lake lamprey (Fig. 34 A). It 

 will beseen that this ovum is even larger than the one from the ovary 

 of a lake lamprey six months before spawning (Fig. 29 A). From the 

 appearance of sexual maturity it is believed that the brook lamprey 

 spawns the spring following its transformation. 



Fig. 37. (X 6). Transection of a larval male lamprey, 140 millime- 

 ters long ; caught in November. To show the small spermary and the 

 intestine with a crescent shaped lumen, due to the intruding typhlosole 

 or valve ; no secondary folds are present as in the adult. 



Fig. 38. (X 6). Transection of a larval female lamprey, 150 millime- 

 ters lono- ; taken in November. To show the ovary with the ova and 

 the intestine. It was not cut at the same level as figure 37, hence the 

 spiral valve or typhlosole occupies a different position. 



Fig. 38 A. (X 53). Ovum from the ovary of the same specimen as 

 figure 38. 



Fig. 39. Section of a lake lamprey's nest with a pair of lampreys. 

 The nest is sectioned parallel with the stream ; it is represented in the 

 usual place for a lamprey's nest, just above ripples. 



The female lamprey is represented as moored to a large stone, while 

 the male is backing down stream carrying a stone of considerable size. 

 It will be readily seen that disturbance of the stones at the upper edge 

 of the nest would loosen the sand, and that it would be washed down 

 stream and thus tend to fill the bottom of the nest, as shown. Mingled 

 with the sand at the bottom of the nest are seen numerous ova, indi- 

 cated by white circles. 



Fig. 40. Face view of a creek with two lamprey nests just above rip- 

 ples. In one nest two lampreys are indicated and in the other but one. 

 In the concavity of the stream, where the water flows somewhat slowly, 

 there is shown a deposite of sand and mud. It is in such situations that 

 the larvse live after leaving the nest. 



Fig. 41. (X 8). A medisection or median sagittal section of a larval 

 lamprey, 135 millimeters long. To show the oral tentacles, one side of 

 the velum, and the relation of the velum to the branchial chamber. 

 To be compared with the frontal section shown in figure 52, Plate VIII. 

 B. R. Branchiae. They occupy a common chamber. The B. R. is on 

 the third gill. 



D. L. 'Dorsal lip or hood. Nearly its entire substance is muscular. 

 A^. Single nasal opening. 

 A^. C. Notochord. 

 V. L. Ventral lip. 



VELUM. The right half or fold of the velum. There is a similar 

 one iu the left half of the body. Compare with figure 52 of Plate VIII. 



PIRATE VIII. 



Fig. 42. (X about 1000). Red Blood-Corpuscles of lake, brook and 

 larval lampreys. (From the Neiv York Medical Journal). 



