THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



[SECOND SERIES.] 

 No. 27. MARCH 1850. 



XVI. — On the recent Foraminifera. 

 By William Clark, Esq. 



To the Editors of the Annals of Natural History. 



Gentlemen, Norfolk Crescent, Bath, Dec. 1, 1849. 



There appeared in the f Annals ' for May 1849, a paper of mine 

 on the recent Foraminifera, containing some new facts and hy- 

 potheses on the anatomical structure of these polypi ; a further 

 examination during the summer months of this year has enabled 

 me to confirm the facts I have already made known, to add much 

 new matter, and to afford such rectifications of the hypothetical 

 inductions as will stamp them with their proper value. I per- 

 sist in my view, that all the calcareous organisms styled Fora- 

 minifera are fixtures for life, as is the case with every other 

 polyparium of the calcareous division. I considered the speci- 

 mens alluded to in my first paper decidedly recent, but the pos- 

 session of others which were undoubtedly alive an hour before I 

 received them, has convinced me of my mistake. The first spe- 

 cimens of Dentalina linearis and Marginulina legumen exhibited 

 in the same shell one half hyaline, and the other with the ani- 

 mal remains, from which I concluded that the polypi inhabited 

 only the two or three anterior cells, and the posterior ones were 

 rendered hyaline by the withdrawal of their contents, either by 

 absorption or desiccation ; but it is more probable that the entire 

 shells so often met with, having all their chambers perfectly 

 hyaline, have been cleared out, at least in those species that have 

 decided visible apertures, by very minute parasites, and that 

 where the chambers are partially emptied the enemy has died 

 before its work was accomplished, in consequence of the orifice 

 being closed up by agglutinated fine grains of sand. I confi- 

 dently rely on this explanation, as in long and careful examina- 

 tions of the Miliolida, I have found in them so many variously 

 Ann. if Mag. N. Hist. Ser.2. Vol. v. 11 



