Sponge and the Sponge Fisheries. 157 



Sponges are found abundantly in tropical waters 

 generally, and perhaps nowhere more abundant than in the 

 seas of the Australian islands. They gradually decrease in 

 numbers towards the colder latitudes till they become 

 entirely extinct. They vary much in shape. Some are 

 beautifully shaped like a vase, others are semi-cylindrical, 

 others nearly flat like an open fan ; some are branched like 

 the opened fingers of a hand, and are called glove sponges, 

 and in others these branches seem to be reduced to only 

 one, which is shaped somewhat like a club. These vary- 

 ing shapes may belong to one species, and the differences 

 are due, so far as known, to the fact that the first men- 

 tioned are found in deep water, and they grade, in the 

 order described, up to the last, which grow in much 

 shallower water. 



The commerce in sponges is of considerable impor- 

 tance. From a very elaborate and learned paper in a 

 recent number of the " Memoirs of the Boston Society of 

 Natural History on the North American Poriferas," with 

 remarks upon foreign species, we derive the following 

 valuable information on the characteristics and classifica- 

 tion of the commercial sponges. The great difficulty 

 which is experienced in any attempt to distinguish species 

 results from the extreme susceptibility of all keratose 

 sponges to any change in external conditions. They 

 appear to require for the production of the forms in abun- 

 dance tropical or sub-tropical seas, and attain by far their 

 greatest development in the number of the forms and 

 species in the West Indian seas. The typical forms, the 

 commercial sponges, are essentially confined to the waters 

 of the Caribbean Islands, the Bahaman Archipelago, and 

 the southern and western coasts of Florida in the western 

 hemisphere, and to the Mediterranean and Red Seas in the 



