169 



Canada balsam, and looking through them instead of also looking 

 at them ; or, in other words, that he has trusted to observations 

 made whilst viewing them as transparent rather than as opaque ob- 

 jects. I am well aware, from long experience, of the value of the 

 former plan as an adjunct; it enables the observer to elicit many 

 important points which would otherwise probably escape notice ; but 

 on the whole, the latter mode is even still more indispensable in inves- 

 tigating the contours of the Foraminifera. 



M. Ehrenberg appears to me to have seen some of the internal con- 

 necting necks, and to have confounded these with the external mar- 

 ginal rows of processes, supposing them to have been identical in their 

 nature and functions. 



I am confirmed in these views by several points in his drawings, 

 especially by his outlines of the front aspects of the Geoponus and of 

 a Nonionina (see his Plate 5, fig. 2, a, a, and Plate 6, fig. 1, d). In 

 the former he has represented a series of square marginal oral (?) 

 apertures, where I suspect that none have existed ; and in the latter 

 the one corresponding aperture is omitted, Whereas in Nonionina it 

 is very large and conspicuous. These facts, combined with the vague- 

 ness of the outline, so different from the elaborate finish of the other 

 drawings, leads me to suppose it possible that these two may not be 

 actual representations, but theoretical sketches, — and that, were his 

 specimens examined under good English achromatic instruments, they 

 would be found to belong to the same type as those described in the 

 preceding pages. 



An important question now arises, viz., how are Polystomella; sup- 

 plied with nutriment ? 



I have already remarked that I found no definite traces of foreign 

 bodies, such as the frustules of Diatomace<e, &c, in the interior of the 

 chambers ; and the same negative fact was observed by M. Ehrenberg 

 in his Geoponus. These substances are very common in Rotalia 

 Beccarii, the various species of Rosalince, and other species which 

 have large oral (?) apertures. Their absence from the Polystomella 

 may be occasioned by the smallness and half-closed character of the 

 same apertures in front of the first cell. These apertures may be 

 sufficiently large to admit such food as these simple textures may re- i>u*£***<> 

 quire, and which may be conveyed from cell to cell by means of the 

 narrow necks. 



In addition to this, the fact of the calcareous shell being perforated 

 by a multitude of minute foramina, shows that, as in M. Ehrenberg's 

 species, and as is most probably the case in all the Foraminifera , the 



