4 EECORDS OF THE AUSTRALIAN MUSEUM. 



In order to study the de^•elopment of the j'ouiig, I i-emoved 

 as I thought, the whole of a young family from a large aquarium, 

 where they had been bred, to a small vessel at the Museum. 



I aftei'wards discovered that five young ones had escaped my 

 search and remained in the original aquarium. These grew at a 

 rapid rate, whereas those placed in the smaller vessel showed no 

 increase at all. So marked was the difference that I took one of 

 the former- from my home and placed it with its smaller brethren. 

 It appeared as a veritable giant among them, and had all its fins 

 properl)" differentiated, whereas in the othei-s the}- had not 

 developed beyond the lar^•al stage. 



To say that the later-introduced fish is twice the length and 

 four 01- five times the bulk of the others may give some idea of 

 its relative size, but its greater development may be better 

 appi^eciated when I mention that it took to feeding on the 

 smaller fish, so that now, after a partnership of about three 

 weeks, it is the sole vertebrate occupant of the vessel. 



As regards food, this fish may be said to have had what 

 Semper calls its optimum, and yet about the time it assimilated 

 the last of its companions it was noticeably inferior in size to the 

 other four with which it was previously associated, though tliey 

 had not been so lavishly supplied with food. They had, howe^'er, 

 abundance of water. The i-emoval of the fry j^laced the volume 

 of water for the individual also at its optimum, so that now it 

 appears to have regained its ratio of development. Thus Semper's 

 conclusions receive interesting confirmation. 



I may mention that we have had a tadpole of one of the 

 Hylido', in a small body of water for over a year ; it has grown to 

 a large size, but has never got beyond the lai-val stage. Other 

 larvae left in the pond, whence this was removed, completed their 

 metamorphoses months ago. 



