230 THE EFFECT OF TEMPERATURE 



of both Strongylocentrotus and Echinus plutei, the 

 body length increases considerably with the tempera- 

 ture up to 20.4, when it is more than 20 per cent, 

 greater than in plutei grown at 11.4, but it is prac- 

 tically unaffected by a further rise. In Sphcsr echinus, 

 on the other hand, the optimum temperature appears to 

 be 15.9, and a further rise of temperature acts unfav- 

 ourably. The effects on the arm lengths differ con- 

 siderably more than those on the body lengths. In 

 Strongylocentrotus this dimension is half as long again 

 at 20.4 as it is at 11.4, but in Echinus it is only very 

 little affected. In the Sph&rechinus pluteus, on the 

 other hand, it is nearly four times longer at 23.7 than 

 it is at 11.4. Each organism, therefore, in respect of 

 each portion measured, reacts in a different manner to 

 changes in the temperature of development. 



Some observations of Standfuss * upon the larvae of 

 certain Lepidoptera, show that the effect of tempera- 

 ture on growth is not necessarily in the direction of in- 

 creased size. Thus he found that whtai, as was often 

 the case, the larval period was shortened by raising the 

 temperature, the size of the adult insects resulting 

 therefrom was correspondingly reduced. For example, 

 a pair of A. fasciata, of which the wings measured re- 

 spectively 46 and 48 mm. across, produced three speci- 

 mens measuring only 36 to 39 mm., when the larval 

 stage was reduced to 68 to 87 days, and the pupal to 15 

 to 20 days, by subjection to a temperature of 25 to 

 30. On the other hand, some other eggs from the 

 same original pair of A. fasciata, which, though exposed 



*The Entomologist, vol., xxviii. p. 69, 1895. (Translated from the 

 German by Dr. F. A. Dixey.) 



