XIV, 4. Andrews: Preservation of protoplasmie spinnings. 449 



such time as was judged enough in the given instance , the slide 

 bearing the eggs was again displaced by another of füll thickness, 

 the eggs at once put into pure water in a covered glass box , and 

 presently waslied in many changes of water. l 



As soon as the eggs were safely in fresh water, the osmic 

 saucer was again slipped into the Chamber by the opening it came 

 through before, and, this being closed, all was ready for a fresh 

 experiment. Meantime the eggs just killed were examined to see 

 wliat result had been gained , and a fresh batch looked at to note 

 their stage and general condition before killing. This work must 

 be as quick as possible and it requires considerable practise as well 

 as presence of mind to keep all going in swift and ready sequence. 



In sorae first experiments I suspended a tuft of cotton from 

 the top of the Chamber by means of a pin stuck in some slide-wax 

 placed there. But one could not tlms control well the amount of 

 fumes , and this proved important as well as difficult and delicate 

 of adjustment. Equally difficult was it to determine in any given 

 instance the exact amount of time proper for the eggs to remain in 

 the fumes. Their stay was very short in all cases and reckoned by 

 portions of a minute , but 110 time formula can be given because 

 the conditions to be met varied in each case. 



In dealing with Echinoderm eggs , a second too long in the 

 fumes leaves them too dark , their processes shrunk and hard, so 

 brittle in fact as to be of little use. A moment too little does not 

 thoroughly harden them, leaving the whole mass ünfit to withstand 

 the action of any preserving fluid used. 



Those eggs that had seemed fairly well preserved at Woods 

 lloll, I kept in alcohol, and in Haller's fluid ; the small vials being 

 stopped with cotton where alcohol was used , and immersed in a 

 jar of alcohol to prevent tannin from being introduced. 2 But at 

 the end of six inonths neither preservative could be approved, for 

 those in alcohol were shrivelled, the processes destroyed 5 and those 

 in Haller were macerated so as to be practieally worthless for 

 examination with high powers. At Roscoff it occurred to me to 

 vary the II aller formula by using somewhat concentrated sea-water 



J ) The osmic saucer should be covered with glass at the moment it 

 is slipped out of the Chamber; especially if one is working near fresh 

 material - - which should also be kept well covered by a glass. 



-) For this useful method I am indebted to Prof. T. H. Morgan. 



Zeitschr. f. wiss. Mikroskopie. XIV, 4. 2!) 



