288 



Itoyal Society : — On the Nature of the 



pseudopocliivl orifices, contrasted strongly \\\i\\ th(» largor ami 

 lliii'kor shells of the specimens brought up by the sounding- 

 apjiaratus from the bottom immediately beneath, in which the 

 shells were thick and those orifices obscure. It is obvious that 

 if this extraordinary abundance of (ilobigerine life in the bottom- 

 vater ■uas the result of subsidence from the surface or sub-surfai-e 

 stratum, and was merely prejiaratory to the deposition of the shells 

 on the sea-bed, there should have been a correspondence in size 

 and condition between the floating shells and those lying on the 

 bottom immediately beneath them ; whereas no contrast could be 

 more complete, the imj)ression given by the superficial aspects 

 they respectively presented having beau fully confirmed by sub- 

 sequent careful investigation. 



Prof. AV^yAiUe Thomson and Mr. Murray, who notice this con- 

 trast, attribute it to the death of the shells which have subsided to 

 the bottom — being apparently unaware that the observations of 

 Dr. AVallich, with which my own are in entire accordance, leave 

 no reasonable ground for doubt that it is a consequence of their 

 continued life. For it is clearly shown, by making thin trans- 

 parent sections of the thick-shelled Glohi(/erin(t (an operation 

 M hich needs a dexterity only to be acquired by long practice, and 

 A\hich is much facilitated by an ingenious device invented by Dr. 

 AVallich *), that the change of external aspect is due to the 

 remarkable exoifenous deposit (a rudiment of the "intermediate 

 skeleton" of higher Foramiuifera) which is formed, after the full 

 growth of the Glohir/erina has been attained, upon the outside of 

 the proper chamber-wall — so completely masking its pseudopodial 

 orifices, that Prof. Huxley at one time denied their exist-ence. This 

 deposit is not only many times thicker than the original chamber- 

 wall, but it often contains flask-shaped cavities opening from the 

 exterior, and containing sai'code prolonged into it from the sarcodic 

 investment of the shell. Illustrations of this curious structure are 

 given by Dr. AVallich in figs. 17 and 18 of plate \i. of his ' North- 

 Atlantic Sea-bed ; ' and I here subjoin a representation of it, 



Section of Sliell of Globigerina, 

 showing the distinction between the 

 original proper wall of the chambers 

 and the secondary exogenous de- 

 posit, with the flask-shaped cavities 

 in the latter opening externally and 

 containing sarcode like that which 

 fills the chambers. 



kindly given me by Dr. AVallich twelve years ago, which further 

 * Ann. & Mag. of Natural Ilistory, 18G1, Tiii. p. 58. 



