Gasterosteus aculeatus and G. spinachia. 247 



repelled any attack made on the nest, and quitted not its post so 

 long as I remained/^ 



Mr. Richard Howse, who found three or four of these nests 

 in a pool among the rocks at Tynemouth, a year or two ago, 

 informs me that each was attended by a fish, and that they 

 scarcely ever left their nests, but kept hovering about, atten- 

 tively examining them, and thrusting their projecting muzzles 

 amidst the seaweeds of which they were composed; the fish 

 would occasionally poise themselves close to the nests, and fan 

 them with the pectoral fins in the same manner as the Three- 

 spined species. And, indeed, it is quite evident, from the ac- 

 counts given by these two gentlemen, that the habits of both 

 species, in all that concerns nidification, perfectly coincide ; both 

 guard the nest with the same unwearied perseverance, drive off 

 enemies, make all necessary repairs, fan or ventilate the nest, and 

 keep it in all respects in good order. 



It is satisfactory to observe this exact similarity of habits, for 

 Mr. Couch has changed his opinion, apparently upon insufficient 

 grounds, respecting the nest, which he attributed to the Fifteen- 

 spined Stickleback. He now considers it to belong to the com- 

 mon Shanny {Blennius pholis), arriving at this conclusion after 

 having examined the young hatched from ova taken out of one 

 of the nests. '^ Being from the first,'' says this gentleman, 

 " impressed with the conviction that they were the young of the 

 Fifteen-spined Stickleback, I was much surprised to notice the 

 great difference of their shape from that of their supposed 

 parent, more especially in the parts before the eyes, which, 

 instead of being elongated and slender, were short and round. 

 In consequence of this they were closely examined with glasses, 

 and drawn with the aid of a microscope of low power; and 

 though I failed to detect satisfactorily the ventral fins of that 

 fish (chiefly perhaps from their slender form and transparency), 

 yet, from the declivity of the head, protuberance of the belly, 

 the pectoral fin, and the length of the dorsal and anal fins, 

 which in some specimens were continuous with the caudal, and 

 in others separated by a slight notch, I had no hesitation in 

 referring them to the common Shanny.'' 



Now, the young of the Three-spined Stickleback differ just as 

 widely from the mature fish as the young of the Fifteen-spined 

 species are stated to do ; and what is of still more importance, 

 the differences are of exactly the same kind. In the former, as 

 well as in the latter, the parts before the eyes are short and 

 round, and can scarcely be said to project at all in front; 

 the declivity of the head is consequently great; the belly is pro- 

 tuberant, and the dorsal and anal fins are long and continuous 

 with the caudal. The young of the Three-spined Stickleback 



