490 Sivion Hen^y Gage 



30 one can readily see the difficulty in distinguishing speruiary and 

 ovary. When properly prepared and viewed as transparent oVijects, 

 however, the difference between the sperm mother-cells and the ova is 

 most striking. 



Fig. 29. (X 2^). Transection of a female lake lamprey taken in 

 December, i. e., about six months before spawning. To show the size 

 of the ovary and of the intestine ; compare description of Fig. 27 and 

 28. 



Fig. 29 a. (X 53). A single ovum from the ovary of the same speci- 

 men as figure 29. To show the comparative size and general character 

 of the ovum, with its eccentric nucleus ; also to compare with a sperm 

 mother-cell of the same stage of development. Compare Fig. 27 A. 



Fig. 30. (X 20). End of a lobule of the ovary of the same speci- 

 men as figure 29. To show the general appearance of the ovary and ova 

 about six months before spawning. Also the similarity in appearance 

 of ovary and speruiary at this stage of maturity. Compare Fig. 28 

 with its description. 



Fig. 31. (X '2%). Transection of a male lake lamprey in the breed- 

 ing season, to show the relative size of speruiary and intestine, and for 

 comparison with the spawning female (Fig. 32), and the non-spawning 

 male (Fig. 27), also the enormous dorsal ridge appearing in the male 

 lake lamprey during the breeding season. 



D. Dorsal ridge. 



Fig. 32. (X 2%). Transection of a female lake lamprey in the 

 spawning season. Some of the ova are free. Compare with the non- 

 breeding female (Fig. 29), and the breeding male (Fig. 31). While in 

 the male the spermary is considerably larger at the breeding season, the 

 ovary has far more strikingly increased in size. 



Fig. 32 a. (X 53). Ovum of the spawning lake lamprey. The nu- 

 cleus is obscured by the great amount of food-yolk. This figure is of 

 the same magnification, and is introduced for comparison with figures 

 29 A, 34 A, 36 A, and 38 A, to sliow the difference in size of the ovum at 

 various stages of maturity. It is also at the same magnification as the 

 sperm-mother cells shown in figures 27 A, and 35 A. 



Fig. 33. (X 6). Transection of a just transformed male lake lam- 

 prey taken in October, and about 150 millimeters in length. To show 

 the size of the spermary and of the intestine, and for comparison with 

 a female at this stage (Fig. 34). 



Fig. 34. (x 6). Transection of a just transformed female lake lam- 

 prey, about 150 millimeters long, taken in October. To show the ovary 

 and intestine, and for comparison with the male at this stage (Fig. 33), 

 also with the female brook lamprey (Fig. 36). 



Fig. 34 A. (X 55). Ovum from the same specimen as figure 34. To 

 show the size of the ovum at^the time of transformation, and for com- 

 parison with the ovum of a brook lamprey at the same stage (Fig. 

 36 A), also with a larva (Fig. 38 A). 



Fig. 35. (X 6). Transection of a just transformed male brook lam- 

 prey, about 190 millimeters long, caught in October. To show the in- 

 testine and the spermary, and f^or comparison with the just transformed 

 female brook lamprey and the lake lamprey at the same stage (Fig. 2i2)^ 

 34). It will be noticed that the intestine is relatively smaller than in 

 the just transformed lake lamprey. 



Fig, 35 a. (X 53). Single sperm-mother cell of the just transformed 

 brook lamprey, from the same specimen as figure 35. 



