94 TïÎEUBiA Vol. Ill, 1. 



One Antipathid and a small Sea-anemone make up the Coelenterata. 



The sponges found in the lake consist of cushion-shaped masses growing 

 around submerged branches or covering pumice-stones. 



To the above-mentioned species we will have to add the plankton 

 organisms; tow nettings have been taken by Dr. SUNIER in April 191 Q 

 and the catch has been sent to Europe for determination. 



It will be noticed that the fauna of the lake is very remarkable as it 

 consists of marine-littoral and estuarine species belonging to genera of 

 which representatives are known to live in fresh water, and besides there 

 are many aquatic insects which are purely fresh-water forms, having invaded 

 the lake after 1908. 



It will be of much interest to follow the process going on here; to 

 study how this association of animals will behave and change on account, 

 of the water of the lake getting perhaps less and less saline, and its depth 

 and area also altering in future years. 



Conclusions* 



The present investigation with regard to the fauna of Krakatau is not 

 at all ended. It is mainly a statement of facts on which future researches 

 can be based, but the following conclusions may be drawn already, though 

 the correctness of some of these has to be more thoroughly affirmed by 

 later investigations : — 



1. New land is probably first invaded by winged animals, the dispersal 

 by drifting wood or plants only becoming afterwards of more importance. 

 The same is true as to newly-formed fresh-water or brackish lakes; 

 the first inhabitants belonging to the true fresh-water fauna are winged 

 insects. 



2. Many more species certainly came to the islands than those now 

 present, but the absence of the proper environmental conditions 

 prevented their settlement 



3. The first settlers were doubtless scavengers of decaying vegetable 

 matter, the most suitable conditions existing for this group of animals 



., right from the start. For those feeding on live plant tissue the chances 

 are less favourable, the stage of the flora being in this case of the 

 utmost importance. The most difficult is the settlement for predaceous 

 and parasitic animals, it depending on the occurrence and abundance 

 of the proper host in the right stadium. 



4. The newly-arrived species increase at an abnormal rate as long as 

 their parasites and enemies are absent. On new land at the beginning 

 the number of species is slight but specimens abound. 



5. The question of how far the present fauna of Krakatau is to be 

 considered as normal cannot be settled; it must be still abnormal as 

 long as the flora has not been restored wholly. 



