146 PKOF. ST. GEORGE MITART ON 



Finally to be noticed amongst the soft parts is that mass of 

 delicate sarcodic prolongations, the pseudopodia. These radiate 

 from the deepest part of the extracapsular mass, passing between 

 the alveoli where these are present, and perforating the gelatinous 

 investing coat. They radiate in all directions ; and thus in the 

 compound forms the pseudopodia of all but the superficial zooids, 

 and the inwardly directed pseudopodia of even the superficial 

 oues, pass into the soft mass, between its included alveoli. In 

 those single forms, however, which have a bilateral symmetry, the 

 pseudopodia radiate accordingly, and are commonly longest and 

 most numerous from the long axis of the body. They may even 

 stream forth from the ends only, as. in Diplocomts ; and when the 

 skeleton forms a conical shell with special apertures at its base, it 

 is in the latter situation that the pseudopodia are longest. 



The pseudopodia, like those of the Heliozoa, have generally 

 much persistency of direction and little flexibility. Nevertheless 

 they may bend much and can be retracted, an action distinctly 

 observed by Hertwig in Thalassicolla. In some species granular 

 particles of the sarcode may be plainly discerned slowly streaming 

 to and fro along the pseudopodia. 



These processes appear to branch in some species and not in 

 others and similarly they may or they may not anastomose. In 

 some forms they traverse hollow canals enclosed within parts of 

 the skeleton, appearing at the apices of the spines thus per- 

 forated. 



Their number is generally great, over a thousand in an indivi- 

 dual Thalassicolla. On the other hand, they may be so few that 

 theirnumber may serve as a distinctive character, as in Acanfho- 

 metra. Their length may more or less exceed the diameter of the 

 body, as in Ethmosplicera and others, or scarcely equal to a quarter 

 of that diameter, as in Trematodiscus and Spo7tgocyclia. 



In a few bilaterally symmetrical genera {Euchitonia, Spongo- 

 cyclia, and 8pongastericus) there is a flagellum attached to the 

 middle of one end of the body. It is formed of homogeneous 

 sarcode, and is much thicker than the pseudopodia, which it may 

 but very little exceed in length, though it may much exceed them. 

 It has the form of a very elongated cone, and is generally bent in 

 a double flexure instead of being straight like the pseudopodia. 

 It appears to move slowly. 



In Acantliometra and its allies the sarcode, after death, becomes 

 retracted, so as to form blunt prominences corresponding to the 



