98 Great Britain Natural History. 



different ways ; thus the smelt affixes its ova to planks, stones, &c., near high-water mark ; the 

 salmon and trout cover theirs with gravel, while the grayling deposits it on the bed of the river. 

 Perch and most carps attach their eggs to water-weeds, sticklebacks construct a nest, while in 

 the tufted gilled fishes, represented by the pipe- and horse-fishes, the male undertakes the 

 functions of a nurse, the eggs for this purpose, up to the period of the evolution of the young, 

 being retained between the ventral fins, as in certain pipefishes (Solenostomus), in tail pouches 

 as in horse-fishes (Hippocampus}, or in receptacles on tne breast or abdomen as in the pipe- 

 fish (Daryrhamplius), or merely in two rows in the same position as in Nerophis. The males 

 of some tropical sheat fishes or Siluroids also perform maternal duties by carrying the eggs 

 about in their mouths until the young are hatched. In some forms, as lampreys, the expulsion 

 of the roe is mechanically assisted by the two parents fixing their sucker-like mouths to a 

 convenient rock and entwining themselves round one another. Also in carps, as in the 

 common goldfish, the male has been observed to roll the female over and over at the bottom 

 of an aquarium until her eggs have become expelled. Hybrid fishes are likewise deserving 

 of great attention, as in fish culture crosses between the trout and the charr have proved 

 most successful, while the stocking of fresh waters by artificial means, and latterly the sea. 

 are among the most satisfactory accomplishments of modern fish culturists and naturalists. 

 Young fishes for varying periods after birth are sustained by the nutriment contained 

 in the yolk of the egg or dependent umbilical sac, and during this period they have numerous 

 enemies watching to make them their prey. Unable to stem strong currents, they are 

 generally to be found concealed near the sides of streams or ponds, or else under the shade 

 of stones, leaves of water plants and grasses ; while the marine species are among the algae 

 in the sea, or disporting themselves in the sunshine, and these places may be considered 

 their nurseries, which should not only be left . undisturbed, but protected from predaceous 

 foes. As the yolk sac becomes absorbed, the fry of fish have to seek for their food, whether of 

 a minute vegetable or animal character, and it is then that the eggs and young of other lower 

 classes of animals (the invertebrata) become invaluable for their subsistence. In some places 

 around our coasts or in fresh or brackish waters are various kinds of sea- weeds or algas which in 

 the sea decrease in abundance with increasing depth, or should they drift into deep water 

 they fall to pieces, sink and form the basis of soft black mud in which many forms of inverte- 

 brates find their food, while in their turn they afford sustenance for fishes. Besides sea- weeds 

 being useful along our coasts as providing food for fishes, places for depositing their spawn, 

 nurseries for sheltering and rearing the fry, there are likewise forms some of which are micro- 

 scopic, floating in vast quantities over the surface of the deep sea, as the so-called Sargassum or 

 gulf weed. Sponges, in both their fresh-water and marine kinds, and which equally belong to 

 the group Protozoa, were long considered by some authors to be vegetable, by others to be 

 animal organisms. The horny skeletons of some species are exceedingly useful for domestic 

 purposes, while those of commerce are to a great extent brought from the Grecian Archipelago, 

 the Bed Sea and the Bahamas, where they are obtained by divers. Many of the Ccelenterata, as 

 the compound colonies of the fixed and plant like sea firs (Sertularidai) and their allies, are 

 found in our seas, some in large quantities, and they are consumed by fish and other marine 

 animals. There are also in this group the jelly-fishes, medusae, which during the summer and 

 autumn months are found floating in the ocean around our coasts, and occasionally under their 

 umbrella-like discs young fish have been observed to obtain refuge from the pursuit of their 

 enemies. Corals among the Actinozoa in many ways hold a most important place, while their 

 hard structures are exceedingly diversified and interesting. Commercial forms are principally 

 obtained from the Mediterranean, the Red Sea, Persian and Arabian Gulfs, the Mauritius, the 

 Islands of the Malay Archipelago, Japan, &c. ; while the reef-constructing species are distri- 

 buted, and can only exist where the mean temperature of the sea is not below 66. The coral 

 reefs are classed as forming Fringing reefs, Barrier reefs and Atolls. These reefs are largely 

 frequented by fish, some of which possess most gorgeous colours, biit in many instances it 

 has been obsef ved that the flesh of those obtained from such localities is frequently poisonous. 

 Among the jointed Annuloida the term entozoa has been frequently used for the purpose 

 of designating internal parasites. Epizoa on the other hand is the term employed for certain 

 small Crustaceans which, in their adult stage are likewise parasitic upon the exterior of fish ; 

 they possess; a suctorial mouth and limbs furnished with hooks, suckers or bristles. Mollusca, 



