22 HANDBOOK OF INVERTEBRATE ZOOLOGY. 



retracted the peristome and disc, and have secreted a 

 thick layer of cuticle, or a cyst, around the spherical body. 

 They sometimes become encysted while on a stem, or they 

 may separate from the stem first. The encysted forms 

 may retain their vitality for an indefinite period with- 

 out food or moisture. Encystment sometimes takes place 

 after conjugation, and, sometimes apparently without con- 

 jugation. 



V. CALCAREOUS SPONGE. 



(Grantia [Sycandra] ciliata). 



The comparative simplicity of the structure of this 

 sponge (Grantia ciliata) renders it peculiarly available 

 for laboratory work. 



It is a small, light-brown, nearly cylindrical, calcareous 

 sponge, from half an inch to an inch long. Isolated indi- 

 viduals are sometimes found, but it is more frequently 

 found in small crowded clusters ; and each large sponge 

 usually carries smaller ones, which have been formed as 

 buds around its base. 



It is quite common on the New England coast, in shaded 

 places, at or near the low-water mark, upon piles, stones, 

 or shells, as well as upon other sponges, hydroids, and 

 tunicates. 



The sponges should be placed in preserving fluid as 

 quickly as possible after they are collected, and, if it is 

 necessary to keep them alive longer than a few minutes, 

 they should be placed in as great a quantity of fresh sea- 

 water as possible, and kept shaded from the sun. 



Some of the specimens should be preserved in alcohol, 

 to study the general form and the arrangement of the 

 calcareous skeleton ; and others should be preserved in 

 picric or chromic acid for histological work. 



