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 hepatice 
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. Allman also read a paper on the external anatomy of 
Chelurus, Phil., a genus of 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. Mullins, 
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 Wiegmann’s Archiv. fiir Naturgesch., 1839. 
