GENERAL LIFE HISTORY OF THE TADPOLES 35 



as great as iii 1947, aiid also that by the middle of June the 1948 tadpoles 

 were about twice the weight of those in 1947 at the same date, and 

 considerably larger than those in Dagger Lane on the same date. 



(r) 1949 (Fig. 10). Several hundred clumps of spawn had been laid 

 on 2nd April, not at the same place as in other years, but still in the 

 same region of the pond. On i6th April, much of the spawn was 

 spoiled. (This may have been another instance of the spoilage that 

 follows late spawning, as discussed in Chapter i, for 2nd April is a 

 late date for this area.) Only one tadpole was seen at "Spawn Site" on 

 23rd April, but there were a few at "West." As in 1948, the tadpole 

 population was low throughout the season. Tadpoles could always be 

 collected in small numbers at "West," but at no other place after the 

 first few visits of the season. Fig. 10 shows the poor progress made by 

 the tadpoles at "Spawn Site" up to the last date when they could be 

 found there at all. At "West," however, they began to grow rapidly 

 after this date, and on 9th July, the average weight was over 900 mg. 

 The collections from lothjune to 9th July contained tadpoles weighing 

 a gram or more, weights not often exceeded in this investigation. 

 Metamorphosis was beginning in July, and on i6th was still in progress, 

 but many of the Uttle frogs were found dead in the water at the foot 

 of the wall. 



Reviewing the events in Lower Parkfield, it can be seen that the 

 steady progress found at Dagger Lane was absent in all three seasons. 

 When many tadpoles survived the first few weeks, they fared badly 

 afterwards. When disasters thinned the population in the early days, 

 the survivors fared well. The contribution of Lower Parkfield to the 

 total frog population of the area was probably always small. 



With these two ponds described in detail, I now include a shorter 

 account of two other ponds, each one resembling one of those already 

 described. 



Hospital Pond 



This pond (Figs. 11 and 12) was observed in two seasons, and on the 

 whole the events resembled those at Dagger Lane, except diat the 

 growth rate was more rapid until about the later half of May, and then 

 in each year slowed down so that the later tadpoles were not con- 

 spicuously large. Moreover, metamorphosis was noticeably late. In 

 1949, the number of clumps of spawn was larger than I have ever 

 known in one pond, and I estimated that the aggregation contained 



