CONTACT ORGANS IN KILLIFISHES OF WOODS HOLE. 175 



free margin. The only scales with entirely free margin shown 

 here are certain small ones on the snout. On top of the head, 

 however, there are several large plates with the entire margin 

 free. 



On the Fins. Fig. 9 is a camera drawing showing the distri- 

 bution of the organs on the anal fin of a large male F. majalis. 

 It will be noted that they are largest and most numerous on the 

 ends of the rays of the small ventral lobe, the part most closely 

 pressed against the body of the female in spawning. They occur 



FIG. 9. Camera drawing ( X 4) f the ventral fin of a very large male F. majalis. 

 The preparation was cleared in strong KOH solution. 



as branches from the bony fin rays, usually one or two to the 

 joint, and frequently form clusters at the distal end of the rays 

 where branching is occurring. Fig. 10 shows a condition of this 

 sort on one ray of the fin shown in the previous figure, where it 

 was impossible to show all of the elements in the terminal cluster. 

 The portion represented in solid black is the bony portion. It 

 will be noted also that the majority of the contact organs are 

 slightly hooked toward the base of the fin. This position should 



