Observations on the Tliree-Sjnned Stickleback. 7 



dually being absorbed, the spots on the body show less serrated 

 edges, and are deeper in colour ; the entire surface of the fish 

 is stained rather than coloured a cinnamon brown ; the envelop- 

 ing membrane is much reduced in places, especially at what 

 will form the root of the caudal fin. 



On the seventh day the rays of the anal fin begin to 

 appear, sis imperfect rays of a brown colour being visible under 

 the microscope; the lower jaw alone maintains its trausparency. 

 On the eighth day, the markings of the anal fin are more per- 

 fect, the membrane is much narrower, except where the spines 

 and fins in the adult fish are seen ; four days after this, or on 

 the twelfth day, the first formation of the caudal fin is seen, also 

 the protrusion of the ventral spines. 



Notwithstanding a daily change of water, on the thirteenth 

 day my infant sticklebacks were attacked by a parasite, in- 

 visible to the naked eye, but, when magnified, it was ad- 

 hering to the membrane which still encircled the fish. This 

 membrane showed clearly the ravages of the invader, being 

 torn in several places, and by this I lost my whole stock, losing 

 first their activity and in twelve hours, life. 



It was my intention to have ascertained how long after 

 fecundation the ova remain before the fry are hatched, and 

 the different periods that elapse in the development of the 

 dorsal and ventral spines, and also the dorsal, caudal, and anal 

 fins ; this I am obliged to defer to another season. I have, 

 however, seen enough to prove that the delightful study of 

 pisciculture may be successfully followed without practising on 

 the ova of valuable fish like the salmon and trout, for quite 

 sufficient resemblance exists between the development of the 

 ova and fry of the insignificant sticklebacks and the king of 

 fresh- water fishes, that he who studies the inferior may easily 

 understand the greater. 



