86 



1 >1. II. M. YrllKUI. 



incuts, a iv -iv< in the accompanying table, those of the old series 

 1 icing the i : .several observations : 



Here it will be seen that, on an average, a more unfavourable effect 

 was produced by exposure of the ova to a temperature of about 25'5" 

 for an hour or a minute at the time of impregnation, than to one of 

 about 8". Thus 5'7 per cent, diminution was produced in the 10 ob- 

 servations at 25-5, and only 3'9 per cent, in the 14 at about 8. 



All these observations were made on the pluteus of Strongylocentmti/* 

 lividus. A further series was also made with the pluteus of Sphcerechiiiux 

 <irnulnm. This was found to be a somewhat less variable and less 

 reactive organism, but even in its case a most distinct effect was pro- 

 duced. The dimension measured in this larva was likewise the body 

 length.* The results obtained were the following : 



For figures of these larvae, vide 'Phil. Trans.,' B, 1898, p. 468. 



