3 8 VITREO US FORAMINIFERA. TART in. 



bers straight through, the shell, and ending in pores on 

 its surface. According to microscopic measurement the 

 tubes in the Rotalia, which are the largest, are on an 

 average the T oVo ^ an ^ nc ^ * n di ame ter, and as they 

 are somewhat more than that apart, the transparency 

 of the shell appears between them and gives the surface 

 a vitreous aspect. The pseudopodia of the animal have 

 been seen to pass through every part of the wall of the 

 chambers occupied by it ; the apertures of the tubuli in 

 this case are wide enough to permit particles of food to 

 be drawn into the interior of the shell. But threads of 

 sarcode of extreme tenuity alone could pass through the 

 tubuli of the Operculina, which are not more than the 

 __i__ of an inch in diameter, and the distance between 

 them not much greater, which gives the shell an opaque 

 appearance. Particles of food can hardly be small 

 enough to pass through such tubes into the interior to 

 be digested. Dr. Carpenter, however, is almost certain, 

 from the manner in which the animal repairs injuries 

 done to its shell, that the semi-fluid sarcode extends 

 itself at certain times, if not constantly, over the exterior 

 of the shell, as in the Gromia ; and therefore it is by no 

 means impossible that the digestive process may really 

 be performed in this external layer, so that only the 

 products of digestion may have to pass into the portion 

 of the sarcode occupying the body of the shell. 



In such many-chambered shells as are pierced by 

 tubuli wide enough to permit particles of food to be 

 drawn into the interior, each segment of the animal, 

 being fed within its own chamber, has a life of its own, 

 at the same time that it shares with all the others in 

 a common life maintained by food taken in through the 

 mouth of the shell. There are many instances of this 

 individual life combined with a common life among the 

 lowest tribes of animals. 



Although the Perforated order contains types widely 



