STUDYING THE HABITS OF FISHES. II3I 



pressed against her ventral surface. The female always has her head up and 

 her tail down as shown in the figure, but the positions of her dorsal and ventral 

 surfaces with reference to the body of the male may be the reverse of that shown. 

 The movements of the fish are so rapid that it requires many observations on 

 each part of each fish before the observer can be sure of accuracy. 



A close examination of a breeding male of the dace is necessary to show the 

 means by which he retains his brief hold of the female in spite of the slipperi- 

 ness of the skin of both fishes. If he be so examined, it is found that those 

 parts of his body which are in contact with the body of the female during the 

 embrace are beset with minute, sharp pearl organs, and are thereby rendered 

 rough, like a piece of sandpaper (fig. 5, text). The opercular region, covered 

 with close-set pearl organs, has a shagreen-like feel. The sides of the body 

 and tail from the caudal edge of the dorsal fin backward are provided with 

 minute organs which occur in rows along the slightly everted edges of the scales 

 and roughen the surface over which they are found. Finally the upper surfaces 

 of the pectoral fins are provided with close-set organs of moderate size which 

 form rows along the fin rays. By means of these organs the male, whose body 

 would otherwise be smooth and slippery, is enabled to make effective his brief 

 hold of the female. This is the more necessary to him since his scales are 

 devoid of the tooth-like points which occur along the free edges of the scales 

 (ctenoid scales) of many fishes and render their bodies rough to the hand. 



While the female is held in the embrace of the male she emits a few eggs, 

 and with field glasses these may often be seen falling slowly through the water 

 until they rest on the gently sloping end of the gravel ridge or on the adjacent 

 bottom of the pit. Probably not more than 25 to 50 eggs aVe emitted at one 

 time. The released female then floats for a moment belly up as though dead, 

 while the male appears to examine the falling eggs. (Fig. 16, pi, cxx.) The 

 female now speedily recovers and disappears along the neighboring bank, but 

 after a short time returns to the nest and repeats the spawning. She continues 

 this intermittent egg laying until all her eggs have been deposited. She may 

 thus place her eggs in one nest, but more often she deposits a part of them in one 

 nest and a part in another. Meantime, during her absences, other females 

 have entered the nest and laid their eggs, so that when the eggs of any nest are 

 examined they are found to be of several different sizes corresponding to females 

 of different sizes that have entered the nest. 



When the females are not in the nest the male continues to carry stones 

 and thus lengthens the gravel ridge. The eggs that have fallen on the end of 

 the ridge or into the pit just at its base are thus covered by the added stones 

 and included in the ridge. As one female succeeds another and as the gravel 



