420 



calyptra by a mass of loose, succulent, cellular tissue. At the 

 period of dehiscence this mass becomes rapidly enlarged, appa- 

 rently by engorgment of fluid, and, by acting against the more 

 resisting receptacle, forces the sporangium with its pedicle 

 through the mouth of the calyptra, beyond the margin of the 

 receptacle. The peculiar spiral cellular tissue of the sporan- 

 gium is thus brought into direct contact with the atmosphere, 

 and the hygroscopic properties of this tissue placed in a con- 

 dition for manifesting themselves. The result of this is the 

 dehiscence which takes place in the exposed portion of the 

 sporangium, in consequence of the balance of tension in the 

 opposite walls of the cells being disturbed. The author was, 

 moreover, of opinion that the presence of elaters in the hepaticse 

 might be accounted for by supposing the separation, in an early 

 period, of certain cells from the sporangium walls ; that these, 

 falling into the cavity, retain for a certain time their inde- 

 pendent vitality, and become developed into the peculiar or- 

 gans in question, lying at last free among the spores. He could 

 not assent to the doctrine so generally promulgated, that the 

 elaters assist in the dispersion of the spores. 



Dr. AUman also read a paper on the external anatomy of 

 Chelurus, Phil., a genus oi Amphipodous Crustacea, destruc- 

 tive to submarine timber works. 



In this communication the author gives a detailed descrip- 

 tion of the external anatomy and zoological relations of an 

 amphipodous crustacean, recently discovered by Mr. MuUins, 

 C. E., in the timber jetty at Kingstown Harbour, where it has 

 been doing a vast amount of mischief by destroying the timber 

 of the submarine works in that locality. It proves, on inves- 

 tigation, to be referable to a genus established by Philippi, 

 under the name of Chelurus, for a crustacean discovered by this 

 naturalist at Trieste.* The Irish specimens, however, differ 



• See Wiegraann's Archiv. fiir Naturgesch., 1839. 



