BRITISH NULLIPORES. 235 



Nullipores are calcareous deposites. Schweigger considers 

 them to be zoophytes which become calcareous immediately 

 after their birth. As a proof of his'opinion he tells us that 

 after having put the Nullipores into hydrochloric acid, there 

 still remained a gelatino s im Iv with the original form of 

 the Nullipores. I have never found this to be the case, al- 

 though I have dissolved a very great number of \ullii)<)rep ; 

 all that remained was reduced to some membranous morsels 

 contained in the under part y which the Nullipore 



had been attached. These morsels, moreover, appeared diffe- 

 rent from the gelatinous membranes obtained after dissolving 

 the true corals; and we do not obtain them from fragments of 

 the Nullipores if broken from neir the edge. All the Nul- 

 lipores I have broken have had some cavities which pene- 

 trated pretty deep into the branches, and have exhibited a 

 structure very similar to the Osteocolla or calcareuus tufFa 

 which is deposited upon rushes and other plants in lakes and 

 stanks. In my opinion the Nullipores are nothing else 

 than a similar calcareous deposit formed upon marine plants." 

 Link in Ann. des Sc. Nat. n. s. part. bot. ii. p. 330-31. 



To this explanation of the origin of the Nullipores I can- 

 not bring myself to assent. On dissolving several Nulli- 

 pores in weak acids I found, as Schweigger had done, that 

 a subgelatinous base remained retaining the form of the ori- 

 ginal, and exhibiting a very distinct cellular structure, ex- 

 actly indeed the same in kind as that presented to us by the 

 Corallines. The solution of others, referable to N. poly- 

 morpha, destroyed the figure, and left behind merely frag- 

 ments of membrane, but the transition from the one kind 

 into the other is so gradual, that I cannot suppose their ori- 

 gin to be the result of two different causes. On the me- 

 chanical theory it seems also difficult to account for the 



