EELATIVE VIABILITY IN MAMMALS AND BIRDS. 429 



With these comments I shall now pass to exa.mination of the 

 records, which however imperfect aiibrd a considerable body of 

 information *. , 



MAMMALIA t. 

 QUADRUMANA. 



Average Maximum 



Family S1MIID.E. /] ■™^^' i°* .duration, duration, 



•' individuals. 111 niontlis. in months. 



Anth7'opopUhecustroglod2/tes{Chim- 20 8 46 

 panzee). 



A.calvus 2 61 94 



A. gorilla (GoviWa) 2 3'5 5 



Simia satyrus (Orang) 20 5 '5 21 



i7?/Zo6rt^es (Gibbon), whole genus. .. 39 9 51 



H.hoolock 9 17 51 



H.lar 16 4-5 12 



H. agilis 2 5-5 9 



H. leuciscus 6 9'1 29 



H. leitcogenys 1 7 7 



H. muelleri 2 2-5 4 



IT. pileatus 1 6 6 



I£. sijndactylus 1 9 9 



H. hainanus 1 13 13 



We know that tlie figures in the third column are very much 

 below the potential longevities of these animals, whilst the 

 differences between the second and third columns are equally 

 notable. It cannot be doubted that the conditions during the period 

 in question were unfavourable to anthi-opoid apes. In 1901, after 

 the period to which these figures relate, the existing house for 

 Anthropoid Apes was completed. The new conditions differed from 

 the old in providing more space, better ventilation, and protection 

 from improper feeding by the public. These changes have been 

 beneficial ; in the case of the chimpanzee, of the orang and of 

 the gibbon, there is at present alive in the Gardens at least one 

 individual that has lived longer with vis than the longest-liver of 

 the previous period. On the other hand, the average duration 

 has not risen notably. These animals must be regarded as of 

 relatively low viability, a conclusion perhaps less surprising if it 



* Since this paper was written I have seen the extremely interesting " List of 

 Animals," living in the Zoological Gardens at Giza, near Cairo, 2nd Edition, and 

 published in 1910. The author, Capt. Stanley S. Flower, has made the useful 

 innovation of inserting opposite each species a note of the maximum ascertained 

 length of life of an individual specimen in the Gardens. I have added to 1113' paper 

 some of Capt. Flower's records, but as these cover a period of only 12 years, higher 

 maximums were impossible; if he were to publish average durations and state 

 the general conditions of captivity of the different species, the work would be 

 invaluable. 



t The names used in this memoir, as far as possible, are those employed in the 

 ninth edition of the " List of Vertebrated Animals now or lately living in the 

 Gardens of the Zoological Society of London " ; 1 have used Trouessart for 

 determining synon^-ms. 



