THE LIFE-HISTORY OF THE FORAMINIFERA. 177 



which may have hitherto escaped notice, but to lay before 

 you certain conclusions respecting the life-history of some 

 of the Foraminifera which I believe may be fairly drawn 

 from an examination of their dead shells. This is a subject 

 which appears to me not to have received all the attention 

 it deserves, and I am satisfied that these empty shells are 

 capable of affording still more information than they have 

 yet given, since from their nature they retain permanently 

 the impression of any passing condition of the animal at 

 the time of their formation. In the first place, it is evident 

 that the soft and yielding body of the Foraminifer acts as 

 a mould upon which the shell is formed, and that it must 

 remain still and without change of shape while the process 

 goes on ; it follows, therefore, that this formation of shell, 

 so far as the foundation layer is concerned, must be looked 

 upon as a single act, and probably one requiring no great 

 length of time. But if the shell be moulded on the surface 

 of the animal, as I conclude it must be, it is clear that from 

 the first the animal will completely fill it, and whatever 

 growth afterwards takes place must be continued outside. 

 This is evidently the case in the many-chambered Fora- 

 minifera, such as Rotalina, where an additional chamber is 

 formed from time to time to protect the new growths ; but 

 what provision is made where the perfect shell always con- 

 sists of only a single chamber ? The Dogs Bay sand, and 

 especially Mr. Parry^s sample, contains in great abundance 

 two forms of Foraminifera which I believe give some in- 

 formation on this subject; these are Orbulina universa and 

 Globigerina buUoides, — the former consisting of a hollow 

 sphere, with many small perforations, and frequently a 

 single larger one ; the latter of a graduated series of small 

 spheres attached together, and arranged in a helix-like 

 form. These objects are interesting as being the prevailing 

 shells in deep-sea dredgings, and they have been noted as 

 abundant in the bed of the sea under the Gulf Stream -, 



SER. III. VOL. III. N 



