﻿102 



Cincinnati Society of Natural History. 



immense deposit is thickest in Suabia to Franconia, but thins out grad- 

 ually as it extends through Switzerland and Bourgogne ; in Suabia there 

 are rocky walls and cliffs many hundreds of feet high where no stone can 

 be turned without exhibiting traces of sponge structure. 



No very satisfactory classification of the sponges has as yet been made, 

 although many recent writers have attempted, with more or less success, 

 to arrange the very numerous forms now known into definite groups. 



With a few exceptions, all sponges contain spicules. These are either 

 silicious or calcareous. We may, therefore, divide the sponges into two 

 sections, the first being called Calcarea. Skeleton chiefly composed of 

 calcareous spicules, which are generally three-rayed. All the species are 

 marine, and none appear to attain large dimensions, while some of the 

 very smallest sponges known belong to this section — Grautia Compressa, 

 one of the commonest British sponges, will serve as an example. 



The second section is called the Silicia. Skeleton mostly horny, most 

 frequently strengthened with silicious spicules ; these are sometimes ab- 

 sent, and, in at least one genus, the sarcode becomes not even differentiated 

 into a horny skeleton. The sponges belonging to this section are found 

 both in fresh and salt water. Prof. Schmidt proposes to divide it into 

 three divisions : 



1. Where the spicules assume a sex-radiate type. To this will belong 

 some of the most remarkable and beautiful sponges, as the Euplectella. 



2. Where the spicules are anchor-shaped, or of a pyramidal form, con- 

 taining many very familiar genera ; especially the genus Spongilla, met 

 with in fresh water. 



3. Where the spicules are monaxial, polyaxial, or wanting; here, amongst 

 a host of genera and species, would be placed the genus Spongia, to one or 

 more species of which the various sponges known as sponges of commerce 

 must be referred. 



Probably the most beautiful and curious of all sponges are those known 

 as the Glass Sponges. As early as 1835, the distinguished naturalist, Von 

 Siebold, brought from Japan some curious wisps of glass hair measuring 

 about twelve inches in length. Similar specimens were subsequently sold 

 as seaweed by the Japanese curiosity mongers to European tourists and 

 seamen. One end of these wisps was usually inclosed in a leathery sheath- 

 ing and stuck into a piece of coral. Japanese ingenuity lends itself so 

 freely to the concoction of impossible monsters, that anything strange, in 

 the way of a natural curiosity, from that country is regarded with distrust. 

 Combinations so skillfully made as to defy detection, except at the hands 

 of the comparative anatomist, have made naturalists wary. 



