IN THE MUD OF THE LEVANT. 37 



chloric acid. This specimen assists in the illus- 

 tration of one peculiar point of their history, 

 about which it appears to me that Ehrenberg is in 

 error, or at least that his choice of illustrations will 

 lead to error in others. Speaking of the Nautilus 

 orbiculus and analogous organisms, (see page 32), 

 and of the orifices in the calcareous portion of 

 these animals, he refers, in illustration, to the 

 dendritic calcareous particles of Alcyonium and 

 other similar forms, which, by a contraction of 

 the skin, close up the external openings, and 

 hence he comes to the conclusion, that, amongst 

 Foraminifera, the calcareous cell is in fact the 

 dried up skin of the animal. Had he concluded 

 that, as in the case of the shells of mollusks, the 

 skin was the chief instrument in the secretion or 

 assimilation of the compound of calcareous and 

 animal matter, which constitutes the shell, it would 

 have agreed with my own observations ; but the 

 inference to be drawn from his language is, 

 that the external shell is the skin itself— the 

 outer and harder integument which binds the 

 soft internal organisms, and which is strengthened 

 in the perfect animal by dendritic portions of 

 carbonate of lime, which, on the alternate expan- 

 sion and contraction of the cuticle, have the 

 power of opening and closing the foramina. 



