34 



INVEKTEBIfATE ANIMALS. 



closely to the Foraminifera ; ami the resemblance between the two 

 groups is still further increased by the fact that the jjseudopodia 

 often run into one another so as to form a network, and sometimes 

 show a eiiculation of granules along their edges. Theie is generally 

 a central capsule surrounded by a layer of saicotle e.xteriorh', and 

 the latter usually contains coloured cells. A contractile vesicle is 

 usually wanting. _Foui- princijial groujjs of organisms have been 

 described as belonging to the li'-iiUuhtria, and we may briefly notice 

 an example of each of these. 



In the first family we have organisms like Acanthometm (fig. 

 13, a), in which the body is composed of sarcode, supported by a 

 fiamework of siliceous or flinty rods, which all meet in a common 

 centre. The sjiines or rods are all perforated by canals, and each con- 

 veys a pseudo])odium, which is jirotruded from an aperture at its 



Fi;^. l:t.— a Acnnthometra knicolata ; b HaUmnmn h^racaiUJnim, 

 "111- .if the I'ulyaj^Umi (after Mlillev). 



apex. Many pseudopodia, however, are given off from the surface 

 of the body directly, and are not enclosed in the spines. The Acan- 

 thometnE are all minute, and are found floating near the surface in 

 the ojjen ocean, sometimes in great ntimbers. 



In the second family (Poli/ri/stiiix, fig. 13, h) we have a ntnnber of 

 lieautiful little organtsms allied to the Font mi u (fern, but ditl'ering in 

 tlie fact that the body is enclosed in a glassy shell composed of flint. 

 The shell is ].>erforated by numerous holes through which the i>seudo- 

 prjilia are emitted, and it is usually of extreme beauty, being sculp- 

 tured in various ways, and often adoined with spines. The sarcode 

 of the body is usually olive brown in colour, and often does not 

 quite fill the shell. 



Tlie |)seudop)odia are filamentous, and exhibit a slow circulation of 

 granules al(jng their borders, but they do not run into one another. 



