PHYLUM PORIFERA 



121 



Order Heterocoela. — Moderately complex wall. Choanoeytes in 

 radial canals. ScypJia (Grantia). 



Class Hyalospongiae. — Sponges which possess siliceous spicules 

 with three axes and six rays or a multiple of six. Spicules are 

 white and like spun glass. Often called glass sponges because of 

 this skeleton. Venus's flower 'basket. 



Class Demospongiae. — Forms which have either nontriaxial sili- 

 ceous spicules or spongin or no skeleton. They have complicated 

 canal systems and are often quite large and brightly colored. A 

 few fresh-water forms are known. 



Order Tetraxonida. — These are ordinarily attached to the bottom in 

 deep water. Thenea. 



Order Monaxonida. — Includes shallow-water, marine forms and one 

 family of fresh-water sponges (Spongillidae). There are less than 

 two dozen fresh-water sponges known in this country. Spongilla, 

 Haliclona, or finger sponge, and Cliona, or boring sponge. 



^•faiocytes— .•'*•/.;{•• •'I ftatocyiea cong-etfaie 

 •^ '**-••/•* J to jorm gemmates 



inWrgzd^zrnmuka 



K"'-'^ Mi- 



«,'^-*i- 





Fig. 50. — Spongillaj showing reproduction. (Courtesy General Biological Supply 



House.) 



Fresh-Water Sponges 



In the southwestern part of the United States, at least in central 

 Texas, there are four species of fresh-water sponges: Spongilla 

 fragilis, TrocJwspongilla horrida, Asteromeyenia plumosa, and Ephy- 

 datia crater if ormis. Of the four, Spongilla fragilis seems to be 

 the most abundant in this area. Most of the colonies of this 

 species are irregular in shape, averaging approximately % of an 

 inch in diameter; but there are some as large as 6 inches by 2^ 

 inches. Usually they are not over 1/4 of an inch in height. Most 

 of the colonies are irregular in shape, but some are cushion-shaped 

 and a few are branched. Most of the large colonies of sponges in 

 this region are dark grey or chocolate brown in color and are found 



