219 
of some Corals from Fiji. 
branches without twigs, the position of growth may be nearly 
accurately fixed on the dry specimen. Massive species also show 
well-defined characters, but these vary with each genus, and can 
only be learnt by long experience on the reefs themselves. 
Finally I made a rough estimate of the number of polyps 
on some of these coralla, but the method is of little use, as the 
polyps of different species are not all of the same size, nor have they 
necessarily the same method of budding, nor indeed auy connection 
with the volume of the skeleton. It is interesting however to 
note that, while No. 5 gives a sheet almost twice as thick as 
Nos. 1 and 3, it actually has only about half as many polyps, the 
calculated numbers of 3, 3 and 5 being respectively 25470, 23616 
and 12672. Assuming an actual age of 1030 days and a regular 
geometrical progression of 2, periods of 71, 70, and 76 days would 
have elapsed in Nos. 1, 3 and 5 respectively between each set as 
it were of buds 1 . Examined in this way, the numbers of the 
polyps do not seem very large, considering the peculiarly favour- 
able situation of the colonies. It is again suggested that the 
actual time of growth must have been much less than the observed 
time. 
1 I am indebted to Mr J. F. Cameron, Fellow of Gonville and Caius College, for 
this calculation. 
