1885.] NEW-YORK MICROSCOPICAL SOCIETY. 117 



its structure, it became evident that this organism belongs to the 

 animal kingdom. Its exact position in that kingdom has not 

 been fully determined ; but, without stopping at present to con- 

 sider its Protozoan or Metazoan relationships, we may describe 

 it as we know it, — either as a community of animals, or as a 

 communal animal — one from many, or many from one. 



Sponges are found mostly in tropical or warm seas where the 

 water is moderately shallow, although certain forms occur in 

 fresh water in temperate regions. They vary exceedingly in 

 color, shape, and size, yet they can be placed for the most part 

 in a few subdivisions. The classification is not, however, either 

 fixed or entirely satisfactory as it now exists ; still, for all pres- 

 ent purposes, a division may be made into the groups, or families, 

 of the Myxospongiae, Calcispongiae, Fibrospongiae, and Clionidse. 

 This classification is based on the absence or presence of spic- 

 ules in the body-walls of the sponge, and on the composition of 

 these spicules. In the Myxospongiae the walls consist of sar- 

 code, or protoplasm, alone. In the Calcispongiae the tissue is 

 strengthened by calcareous spicules, and in the Clionidae the 

 spicules are siliceous. In the Fibrospongiae the framework of 

 the body is of a fibrous nature, being made up of a substance 

 called keratose. To this group are assigned the beautiful and 

 delicate glass-sponges, although their framework is of silex. 



How do sponges grow ? and what is the first stage of their 

 life-history ? The marine sponges begin life either from the egg 

 or by budding. The fresh-water sponge, besides the develop- 

 ment from the egg, may start from a minute seed-like body, or 

 statosphere, which is formed in autumn in the walls of the 

 sponge, and from which a germ, the true statoblast, emerges in 

 spring to develop into the adult form. Owing to the spicules 

 with which they are adorned, some of the statospheres are very 

 beautiful. The classification of this family is largely based on 

 the shape of these spicules. 



The sponge of commerce is the keratose skeleton of certain 

 members of the group Fibrospongise, all the living substance 

 having been eliminated. We shall better see the difference be- 

 tween the sponge in this condition and the sponge in its natural 

 state, if we first learn how the animal lives. In gazing down 

 into the water in regions where sponges abound, the observer 

 will descry, fastened to rocks and other supports, certain velvety 



