236 tHK ZOOLOGIST. 



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 

 Algse 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 sub- 

 sistence. 



In some places around our coasts or in fresh or brackish 

 waters are various kinds of sea-weeds or Algse 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 invertebrates find their 

 food, while in their turn they afford sustenance for fishes. Betides 

 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 

 microscopic, 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 Eed 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 {Sertulariidce) and their allies, are 



