2064 PERCY SLADEN TRUST EXPEDITION. 
F. fragilis) from the Hawaiian Islands are so different from the specimens of F. patella 
that I prefer to keep them apart, at least for the present.’ In this I agree with Vaughan. 
But Déderlein describes Cycloseris-forms and /Diaseris-forms from the same locality in 
New Britain; and his Cycloseris-specimens are so small, about a third the regular size of 
other such forms of F. patella (to which the Déaseris-specimens approximate in size), 
that they may well be merely stages in their development, as it is obvious that all 
Diaseris-forms probably pass through Oycloseris-stages. 
I am supported in the separation of the Diaseris-form from the Cycloseris-form by the 
fact that the two forms of the same species are seldom known from the same locality. 
Thus I find 7 localities for /. distorta, Diaseris-form, of which Zanzibar and Cargados 
Carajos are the nearest to Aldabra, where its supposed Cycloseris-form was obtained. I 
have already referred to /. patella, for the Cycloseris-form of which six other localities 
are known. As already noted, Vaughan does not agree to the absorption of F. fragilis 
into F. patella, but his two Hawaiian specimens of the former come from a station at 
which 24 specimens of F. patella (Cycloseris-form) were obtained*. In 8S. Nilandu 
Atoll, Maldives, at 25 fins., where we dredged 47 mostly entire specimens of living 
F. distorta, the bottom was practically formed by a rubble of the coralla of this species 
consolidated together. We carefully went over upwards of a hundredweight of this 
material and yet found no Cycloseris-forms, which we were particularly searching for, as 
we had obtained on the same day in a previous dredging, devoid of Déaseris-forms, a 
Cycloseris-specimen of F. sinensis, a widely differing species. Lastly, living Pungia 
are not infrequently hurled over the reefs in storms and hurricanes. Most so moved 
will be broken and carried to positions in which the continuance of life is impossible. 
Some, however, reach a haven of rest. From the structure of their coralla any break 
almost invariably extends from the axial fossa to the edge of the disc. Such fragments 
regenerate the rest of their discs, and it is quite unnecessary to point out the strong 
resemblance of such regenerated discs to Diaseris-forms. 
On the whole, I am inclined to consider that Déderlein’s identifications of Déaseris- 
forms and Cycloseris-forms of the same species of /wngia in only one Group out of his 
seven Groups (the rest of which appear to me to be scientifically correct) is rather forced 
and still doubtful. The question is one which I must leave to future investigators, but 
I venture to suggest that there should be an eighth Group, the Déaseris-group, which 
would contain at present the species F. fragilis, Alcock, F. distorta, Michelin, F'. mortoni 
(Tenison-Woods), and perhaps a species corresponding to the Déaseris-form from New 
Britain described by Déderlein under J’. patella. In correspondence with this change 
I use the term Cycloseris-group for the other forms placed by Déderlein in his 
Patella-group. 
* Of course there is no inherent improbability in a species of Pungia having acquired in any locality a Diaseris- 
form to the complete obliteration of its Cycloseris-form. The two forms live on practically the same food and would 
naturally come into such particularly close competition with one another, that one might be easily killed out in the 
locality by any special suitability of the other, even if very slight, to its biological or physical conditions. In the 
Maldives, Diaseris-forms were dredged only in currents “ generally in or near passages into the lagoons of the atolls,” 
whereas the Cycloseris-forms, both of the Maldivan and of the present expedition, came from relatively still water. 
