228 GENERAL HISTOEY OF THE rNTFSOIlIA. 



Foraminifera to be phytophagous, in consequence of his having detected in 

 some specimens fragments of Diatomaceae, and other simple forms of vegetable 

 life. But as I have di^edged them ahve at a depth of 108 fathoms (which is 

 far beyond the Laminarian zone), and they are extremely abundant at from 

 40 to 70 fathoms, ten miles fi^om land and beyond the range of any seaweed, 

 it may be assumed, T^dthout much difficulty, that many, if not most of them, 

 are zooj)hagous, and prey on microscopic animals perhaps of even simpler form 

 and structure than themselves. They are in their turn the food of Mollusca, 

 and appear to be especially relished by Dentalium entale.^' The assumption 

 that, because the Laminarian zone ceases at a much less depth than that at 

 which Foraminifera occur, therefore no Diatomeae are found, is quite gra- 

 tuitous, and opposed to observation. The notion also that animal life fur- 

 nishes nutriment to Foraminifera at depths where vegetable existence, and 

 where the doubtful Diatomeae cannot be sustained, is opposed to all proba- 

 bihty. 



Of the rate of growth and of the duration of Ehizopoda we have few re- 

 corded observations : we must, however, suppose them regulated by external 

 cii'cumstances, such as abundance of food, moderate temperature, and the like. 

 Schultze observed of 'Foraminifera living in a small quantity of sea- water, so 

 to speak, in captivity, that they grew exceedingly slowly. In only one Po- 

 ly stomeila out of many, kept under observation for several months, did he ob- 

 serve the production of a new chamber. Rotalice, however, were more fre- 

 quently seen in process of growth, the walls of the new-formed segments 

 being extremely dehcate and deficient of calcareous matter. Some very young 

 specimens of MiJiola ohesa were found to produce two new chambers, after the 

 completion of the primary one, in the com^se of four weeks. 



From this fact of their very gradual growth, says Schultze, we may con- 

 clude that a year or more may elapse before the construction of a many- 

 chambered shell is completed. This natui'alist has, indeed, kept the same 

 specimens of PohjstomeUa and of Rotalida in capti\dty for nine months ; and 

 theii' persistence for a much longer period is highly probable. If, he adds, 

 the production of germs put a termination to life, then this phenomenon 

 entails a fixed limit to its duration. Dujardin, again, found Arcellce alive after 

 two years, in a vessel in which he had preserved them. 



The testaceous Ehizopoda possess the power of repaii'ing the efi'ects of me- 

 chanical injimes to their shells. This has been proved by Schultze in the 

 case of the Polythalamia ; and we may conclude the same faculty is possessed 

 by the Monotlialamia. He has seen almost one-half of the shell of Pohjsto- 

 mella strir/ilata, which had been broken away, repaired by a new calcareous 

 wall resembling the normal one both in its pores, eminences, and markings. 

 He also frequently noticed in this same species irregularities in the conforma- 

 tion of the shell, which he attributed to damages previously inflicted ; and 

 experiment showed him that, even on the same day that a considerable portion 

 was removed, the animal set vigorously to work to rei)lace the lost sheU, and 

 protruded its processes just as before. 



Occasionally the destruction of a portion of the shell gives rise to monstrous 

 (abnormal) forms. Thus Schultze noticed a double PolystomeUa strigilata, 

 and Eeuss a monstrous Nodosaria anmdata, which he called N. dichotoma ; and 

 Dr. Carpenter has foimd several " monstrosities of Orhitolites resulting from an 

 unusual outgrowth of the central nucleus." 



The Ehizopoda can, doubtless, maintain life under very prejudicial condi- 

 tions. The power possessed by the sarcode substance, of sustaining existence 

 when even the greater part is torn away, and the capability of repair mani- 

 fested by the testaceous species, are facts indicative of their tenacity of fife. 



