202 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



To one of the phials was added one-third of rain- 

 water, but no immediate change was perceptible. 

 After the mixture had stood for a little, however, 

 it became clearer, with a thin stalk of mucus 

 i^tanding up the middle, and tinged towards the 

 base with a brownish red deposit that had subsided. 

 In a few hours the base of the stalk had spread 

 into a dark mass. 



At the end of two days the unmixed fluid taken 

 from the same test still retained its whitish appear- 

 ance. 



The empty test was put into fresh water, and 

 in a short time a good deal of mucus was found 

 on the outside among the spines. Thinking it possible 

 that the mucus might be derived from water not 

 fully drawn from the test, and to make sure that 

 nothing was left within before the fresh water 

 touched it, I took out the whole of the viscera and 

 washed the inside of the test clean with sea-Avater. 

 It was then put into fresh water, where in a short 

 time it threw out mucus copiously. From other 

 experiments of the same kind, attended with the 

 same results, it appeared that the source of the 

 mucus did not exist within the walls of the shell. 

 I now repeated experiments that I had formerly 

 made of removing all the spines from the outside. 

 In this case I first cleaned off the spines with my 

 knife; and lest any of the minute ones or other 

 organism might be left, I rubbed the test all over 

 with sand, cleaning out thoroughly all the furrows. 

 It was then immersed in fresh water, but no mucus was 

 I)roduced, showing that the origin of that matter was 

 not to be looked for in the test. With a view to find 

 where the mucus issued from, I cleared off a circle of 

 spines, leaving a patch of them on one side of the test, 

 and placed the test in a tea-cup in such a i^osition that 

 when the cup was filled with fresh water the patch 

 of spines would just be covered. By this method, 

 with a good light thrown on the side from which 

 the spines projected, I could see them clearly 



