304 LECTURE XII. 



dorsal fins assume a dusky margin ; tlie lateral bars begin to be con- 

 cealed by a silvery pigment ; and tlie migratory dress, characteristic 

 of the Salmon fry, or ' smolt,' is assumed. The fish now begin to 

 congregate in shoals and to migrate seaward. 



hicuhation. — Eckstroem first published a clear account, in 1831*, of 

 the singular marsupial econoiny of the Pipe-fishes. In the Syngna- 

 thus acus the sexes come together in the month of April, and the ova 

 pass from the female and are transferred into the subcaudal pouch of 

 the male, being fecundated in transitu, and the valves of the pouch 

 immediately close over them. In the month of July the young are 

 hatched and quit the pouch, but they follow their father, and return 

 for shelter into their nursery when danger threatens. 



Aristotle signalises the Phycis, since recognised as a Mediterra- 

 nean species of Gobius, as the only sea-fish that makes a nest and 

 deposits its spawn therein. Olivi confirmed the statement, and de- 

 scribes the nest as being composed of sea-weeds (algi and zostera), 

 adding that the male fish guards the female during the act of ovi- 

 jjosition and the young fry during their development, f 



Dr. Hancock has observed similar habits in certain fresh-water 

 siluroid fishes of Demerara called ' Hassars,' which belong to the 

 genus Callichthys : the Round-headed Hassar forms its nest of grass, 

 the Flat-headed Hassar of leaves. " They are monogamous ; both 

 male and female remain by the side of the nest till the spaAvn 

 is hatched, with as much solicitude as a hen guards her eggs, and 

 they courageously attack any assailant. Hence the negroes fre- 

 quently take tliem by putting their hands into the water close to the 

 nest; on agitating which, the male Hassar springes furiously at 

 them, and is thus captured." Through the kind interest of the 

 Earl of Enniskillen, a trustee of the Hunterian Museum, a specimen 

 of the nest with the spawn and parent fish, has been transmitted 

 to the College and is now placed in the Hunterian series of 

 Nidamental structures (No. 3787. b. b). | 



* See also xxxix. ii. p. 327. f xxiii. t. xii. p. 6. 



^ This specimen was exhibited at the Lecture. 



END OF THE SECOND VOLUME. 



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