BY J. J. FLETCHER. 365 



being brief and well-marked, are more or less prolonged and inter- 

 mittent, a condition for which the irregular character of the 

 rainfall is primarily and mainly responsible. Of a period of thirty 

 years the Government Astronomer says : — '' There is not much 

 difference in the average amount of rain falling in each of the 

 first seven months, but a marked decrease is manifested in the 

 last five, especially September, November, and December. . . 

 It is remarkable that during that period every month in the 

 calendar, except December, has been the maximum for the year 

 one or more times. . . . The evaporation in October, 

 November, December, and January is greater than in the other 

 eight months of the year." (Meteorology of N.S.W. Industrial 

 Progress of N.S.W., 1871, pp. 589, 590). 



That is to say at the season of the year at which it would seem 

 most natural for the frogs to spawn, judging from the habits of 

 frogs in general, the meteorological conditions on the whole are 

 against them, for, even allowing for averages, the monthly rainfall 

 is decreasing, the evaporation is on the increase, so that spring- 

 droughts are by no means uncommon ; this state of things is 

 varied occasionally by a very heavy rain-storm during this period 

 giving the maximum monthly rainfall for the year, an event 

 which gives the frogs special opportunity. 



In the case of Rana temjooraria, for example, all the surviv^ing 

 frogs of the same season's hatching are approximately of the same 

 age, while all the frogs of different ages differ in regard to the 

 same by some multiple of one year. With our frogs this may 

 obviously not be the case, since individuals of the same species 

 hatched during the same season may differ in age by as much 

 as six months or more ; so that it is reasonable to expect that the 

 maturation of the ova, though probably occurring at regular 

 periods, should not be simultaneous in all the females of a given 

 species. Consequently of our frogs it may be said that they 

 spawn when they are ready, or as nearly as the conditions of 

 moisture will allow ; but that they are not all ready at the same 

 time. 



