CLASS CYCLOSTOMATA 



421 



Lampdra wilderi, the brook lamprey of North America, breeds 

 in the spring. Stones are moved by means of the buccal funnel 

 until a space is cleared on the bottom where a number of 

 individuals congregate (Fig. 356). A 

 male clings to the head of a female for 

 a moment, winds his tail about > her 

 body, and discharges spermatozoa over 

 the eggs when they are extruded. The 

 adults die soon after spawning; they 

 probably take no food, and are there- 

 fore not injurious to fishes. 



FIG. 356. Lampetra wilderi, in the 

 act of spawning. (From Shipley and 

 MacBride, after Dean and Sumner.) 



FIG. 357. PalcBOSpon- 

 dylus gunni, a Devonian 

 Cyclostome. (From Dean, 

 after Traquair.) 



A fossil vertebrate, Palaospondylus gunni (Fig. 357), was 

 probably closely allied to the cyclostomes. It was found in 

 the Devonian rocks of Scotland and is about an inch long. 



