IIOUN EXPEDITION — SUMMAHV. 143 



without any attempt at foiicealmont — every animal (if every kind seems so to 

 spealv to forget all else except the necessity of feeding as rapidly as possible and 

 reproducing its species. 



Tiie first phase in tlie struggle for existence is concerned with the development 

 of the ovum. Uidess tiie development he very rapid the animal has no chance of 

 growing to the size at which it can take advantage of the raj)idly disappearing food 

 supply — disappearing not l)ecause tliere is not enough and to spai'c for all hut 

 Ijecause the vegetation on which all depends can only withstand the temperature 

 for a given length of time. The second pliase in the struggle is entei-ed upon 

 when the dry season supervenes, and this is really dependent upon tlu^ first, foi- it 

 is only those who have grown to a certain size and who in addition h.ive haiily 

 enough constitutions who have any chance of lasting out the drought with its 

 miserably small supply of food and water. 



One important point in connection at all (events with the smaller marsupials 

 and probably with all tlie animals to a greater or less extent is, as already noticed 

 in the Zoological report,* " that they attain full siz(> at very varying periods of 

 life and that an animal reared during a successive series of bad seasons and 

 consequent dearth of food may never attain the full size characteristic of the 

 species, though at the same time it may b(»ar young ones." This curious fact is 

 well seen in the case of P/insco/oga/c cristicaiida wiiero the smallest mature male 

 measures (head and body) 13G mm. and the hirgest 220 nmi. ; the smallest female 

 of the same species measuring 12.5 mm. and the largest 170 mm., though both of 

 the latter were carrying young ones in the poui^h. Tn each case the larger forms 

 were obtained at the clrjse of a good season. In the same species the nundjer of 

 teats varies between four and eight, the latter being present again in those 

 capturi'd at the close of ;i good season. 



These facts will serve to show the direct influence which the climate has upon 

 the development of the animals, for no such relatively great vai-iations exist 

 amongst allied species found in the coastal districts where the climate is not lial)le 

 to such irregular fluctuation.s. 



Taking the difTerent groups we may now point out the more important points 

 concerned witli each. 



Jifa/iuiia/ia. — In the Eutheria the most important forms are the large bat 

 {Mrgadcnun ,Q/xns) and the Rodents. The former is only found in tin' caves 



♦ I'art II., )). '2'.. 



