50 Introduction to Animal Morphology. 



species). Myxastrum, also non-vacuolated, marine, multiplies 

 by germs produced by radial fission, each being enclosed in 

 a siliceous envelope. 



CLASS 2. LABYRiNTHULE^:(O6V//('(?r'^'). Nucleated 

 plastides found incrusting marine Algae, consisting of 

 a central granular mass, sending off branching and 

 interlacing fine protoplasm threads, possibly with a 

 differentiated axis, and forming variable meshes with 

 curved outlines. Through these threads, yellow 

 spindle-like cells glide in different directions, and 

 accumulate at certain parts of the thread in clusters. 

 A non-nucleated freshwater form has recently been 

 discovered on Sphagnum in Ireland by j\fr. *\rchcr 

 (Chlamydomyxa).* These myxomycetoid forms re- 

 quire further examination. Reproduction takes place 

 by fission; encystation of the spindles sometimes 

 occurs. 



CLASS 3. RHIZOPODA (Dn jar din}. Indistinctly 

 nucleated plastides, moving by filiform anastomosing 

 pseudopodia, containing circulating granules, vacuoles, 

 rarely one or more contractile vesicles. The yellow 

 or brown protoplasm secretes, near the surface of its 

 mass, a shell with one or many perforations, through 

 which the pseudopodia project, and they generally 

 form an expansion enclosing the shell. The shell is 

 usually calcareous,! but may be siliceous (Polymor- 

 phina, Nonionina), or of agglutinated sand-grains 

 (Textularia, &c.), or chitinous (Gromia), or scarcely 



* Perhaps Pelomyxa (ciircf) is related to these. 



t CaCOs with CajHPO^ in Orbiculina adunca, c. Siliceous spicules 

 have been found in the spicules of Calcarina, Carpenteria, and around the 

 mouth in the sessile conical Squamulina. 



