424 



M. E. COLLETT. 



material for the experiments. The gills were divided into narrow 

 strips of one or two filaments. The larvae were generally helio- 

 tropic and so could easily be secured in large numbers in very 

 little water. Not all the larvae were fully normal: Echinarach- 

 nius, Arenicola and Asterias were the most variable in vitality. 

 All of the solutions used (except of course NaCl) were made up 

 in sea water rather than in distilled water and were never kept 

 more than eight hours : not over four hours in the case of volatile 

 substances. The experiments were carried out in- stoppered test 

 tubes which for higher temperatures were floated in warm water. 

 The temperature of the tubes was read during every experiment. 

 Each day's results were recorded on a separate slip of paper. 

 The summary given below is an average of all observations and 

 where these vary because of temperature, difference in viability 

 (or other experimental error), the order of susceptibility has been 

 verified by reference to the separate experiments in which the 

 conditions must have been the same. The results obtained are 

 as follows: 



In comparing the resistance to saponin with that to hypotonic 

 NaCl it is clear that although there are some irregularities 

 (which are starred), the general order is the same. This is quite 

 unlike the sharp reversal of order obtained with erythrocytes in 

 saponin and in hypotonic NaCl. The order of cilia resistance in 



TABLE I. 



Saponin (per cent, represents dilution of a stock solution of 0.5 per cent, in sea 



water) . 



