522 C YCL OS TO MA TA. 



The spawning takes place in spring, usually far up rivers. 

 Before laying the eggs, the lamprey seems to fast (cf. 



III. 



FIG. 276. The lamprey (Petromyzon marinus). 



I. The entire animal ; note the seven gill-slits of which the first is 

 marked g.s., the nostril ., and the unpaired median fins. 

 II. Ventral aspect of the head; ./., upper teeth; /., lower 

 teeth; /., the piston in the mouth. III. Upper surface of the 

 head ; ., the nostril with the pineal groove behind it ; e. , the eye. 



salmon, Protopterus, frog), and its muscles undergo a 

 granular degeneration (cf. Protopterus, tadpole, etc.). Soon 



