SPONGE WEAVERS. 141 



It has been objected that it is an error to speak 

 or write of these skeletons as interwoven, for 

 there has been no interweaving, and no basket- 

 work, since the material has been produced, and 

 formed, at the same time as the framework, but no 

 other word so well expresses the general appearance 

 of this natural production as one borrowed from a 

 branch of human industry, and it is scarcely pro- 

 bable that it will convey an erroneous impression. 



Large and appreciable as most sponges are to 

 the naked eye, it is to the microscope that we are 

 indebted for a revelation of their beauties, for, except 

 in a few rare and notable instances, their external 

 appearance is by no means specially attractive. 

 Whether we study the singular and variable forms 

 presented by the spicules themselves, or their com- 

 bination and arrangement in the sponge skeleton, 

 they alike afford instruction and entertainment ; in 

 the former case by their great variety and elegance, 

 and in the latter by their adaptability to the special 

 purposes which they are intended to serve. The 

 answer to the question why any given form of 

 spicule should have that particular form, in preference 

 to any other, can only be answered by seeing the 

 spicule in its natural position, and ascertaining what 

 function it had to perform. 



The most Common and numerous forms of spicule 

 are the simple cylindrical, or needle-shaped, if we 



