1 66 PORIFERA 



that is to say, tlie separate organs are of an order of size inferior 

 to that of the entire body. The animals are fixed or lie loose 

 on the sea bottom ; there are in no case organs of locomotion, 

 and again no sense-organs, no segregated organs of sex, and as a 

 rule no distinction into axis and lateral members. It is by 

 these negative characters that the collector may easily recognise 

 a sponge. 



History. — Sponges are, then, in many of their characters 

 unique ; and they present a variety of problems for solution, both 

 of special and general interest, they are widely distributed in 

 time and space, and they include a host of forms. It therefore 

 causes no little surprise to learn that they have suffered from a 

 long neglect, even their animal nature having been but recently 

 estaljlished. Though known to naturalists from the time of 

 Aristotle, sponges have been left for modern workers as a 

 heritage of virgin soil : it has yielded to them a rich harvest, 

 and is as yet far from exhausted. 



The familiar bath sponge was naturally the earliest known 

 member of the phylum. It is dignified by mention in the Iliad 

 and in the Odyssey, and Homer, in his choice of the adjective 

 " full of holes," iroXvTp-qro'i, shows at least as much observation 

 as many a naturalist of the sixteenth and seventeenth centuries. 

 Aristotle based his ideas of sponges entirely upon the characters 

 of the bath sponge and its near allies, for these were the only 

 kinds he knew. Witli his usual perspicuity he reached the 

 conclusion that sponges are animals, tliough sliowing points of 

 likeness to plants. 



The accounts of sponges after Aristotle present little of 

 scientific interest until the last century. Doubtless this is in 

 part due to the absence of organs which would admit of dis- 

 section, and the consequent necessity of finer methods of study. 

 Like other attached forms, sponges were plant or animal as it 

 pleased the imagination of the writer, and sometimes they were 

 " plant animals " or Zoophyta : those who thought them animal 

 were frequently divided among themselves as to whether they 

 were " polypous " or " apolypous." An opinion which it is 

 somewhat diificult to classify was that of Dr. Nehemiah Grew,^ 

 wlio says : " No Sjwnge hath any Lignous Fibers, but is wholly 

 composed of those which make the Pith and all the pithy parts 



' Ilarities belonging to the Royal Society i^reservcd at Gresham College, 1686. 



