SECT. ii. THE SIMPLE ORLITOLITE. 35 



extending through passages which connect the cavities 

 laterally. The segments are also connected radially 

 by similar sarcode bands, which originate in the mass 

 of sarcode filling the nucleus, and extend to the pores 

 in the margin of the disk. The cavities of each zone 

 alternate in position with those of the zones on each 

 side of it. The animal sends out its pseudopodia 

 through the marginal pores in search of food, which 

 consists of Diatoms and Desmidiacese ; they are drawn 

 in, digested without any stomach, and the nutritious 

 liquid is conducted by the gelatinous bands from seg- 

 ment to segment and from zone to zone, even to the 

 innermost recesses of the shell. 



It is supposed that during the growth of the Orbito- 

 lite, when the animal becomes too large for its abode, 

 its pseudopodia coalesce and form a gelatinous massive 

 coat over the margin of the exterior zone, which secretes 

 a shelly ring with all its chambers and passages, each 

 ring being a mere vegetative repetition of those pre- 

 ceding it. That vegetative property enables the animal 

 to repair its shell or add a part that is wanting. For, 

 if a small portion of a ring be broken off and separated 

 from the living animal, it will increase so as to form a 

 new disk, the want of the central part or nucleus not 

 appearing to be of the smallest consequence ; indeed, 

 the central rings are very often imperfect. The sarcode 

 'of these animals is red, and although the shell is of a 

 brownish-yellow by transmitted light, it is so translu- 

 cent that the red tint is seen through it. 



The simple Orbitolite has many varieties. Sometimes 

 it begins its life as a spiral which changes to a circular disk 

 as it advances in age. It varies in thickness, and some 

 of its very large varieties may be said to consist of three 

 disks or stories of concentric chambers and many mar- 

 ginal pores instead of one. The upper and base stories 

 of concentric chambers are alike, the intermediate one 



D 2 



