RELATIVE VIABILITY IN MAMMALS AND BIRDS. 467 



Summary of Marsiqjialia. 



The records show in the first place that whilst within tlie 

 different divisions of Marsupials, there is frequently a close 

 correspondence between size and longevity, there is no such 

 relation if the group be considered as a whole. The maximum 

 duration was that of a Wombat which lived nearly 1 8 years in 

 the Gardens; next comes a Kangaroo with a dui-atiouof 14 years; 

 then some small Phalangers reaching neai^ly 12 years; then a 

 Thylacine reaching nearly 9 years. It is notable that much the 

 best records are in the case of animals which have had good access 

 to air ; the chief exception, and this only a doubtful oiae, is that 

 of the Phalangers. 



MONOTREMATA. fY^ .Av.dm-. Max. dm-. 



liidiv. Ill mouths, in months. 



Echidna Jiystrix (Echidna) 4 1'5 5 



The records are sufficient only to show the failure, in the period 

 in question, to pi-ovide suitable conditions for these animals. 

 They have always been kept in artificially heated houses. 



Summary of Mammalia, 



It is advisable to repeat here that the material on which this 

 communication is based, is defective in certain important respects. 

 No information was available as to the condition of the animals on 

 their arrival. I have tried to eliminate this source of eri-or to a 

 certain extent, by omitting in most cases entries of animals that 

 had lived less than a month in the Gardens. Similarly, no infor- 

 mation as to the age of entrants was available. It is oJdvIous that 

 the heavy incidence of mortality in very yoruig animals is an 

 important factor independent of the special conditions of captivity, 

 whilst the possibility of duration is naturally less in old animals 

 than in young adults. These defects probably have abnormally 

 lowered the records of average and of maximum duration, but to 

 what extent I am unable to guess. At the beginning of 1911, 

 I put into operation a system suggested to me by my friend 

 Mr. J. L. Bonhote, F.Z.S., and I hope that thirty years after this, 

 someone will be in a position to institute an enquiry similar to the 

 present communication to the Society, but based on more exact 

 data. In every case where it is possible, a card is prepared for each 

 new arrival at the Gardens ; on the face is placed the name, and 

 mode and date of acquisition of the animal ; on the reverse is 

 entered the first place of detention, the apparent condition of 

 health, and any indications of age (" very young," " adult," or 

 " old adult," unless exact particulars are known) ; the card follows 

 the animal to each successive house in Avhich it may come to be 

 placed ; the dates of such changes and any important events in 

 its history are noted ; finally, at the Prosectorium, the date and 

 cause of death are entered, with any further data as to age that 

 may be available. 



