56 DEOSEEA EOTUNDIFOLIA. Chap. III. 



of the tentacles, tlie glands secrete less freely, or quite 

 cease to secrete, and the aggregated masses of proto- 

 plasm are then redissolved. Moreover, when leaves 

 are immersed in dense vegetable solutions, or in 

 glycerine, the fluid within the gland-cells passes out- 

 wards, and there is aggregation ; and when the leaves 

 are afterwards immersed in water, or in an innocuous 

 fluid of less specific gravity than water, the protoplasm 

 is redissolved, and this, no doubt, is due to endosmose. 

 Opposed to this view, that aggregation is caused by 

 the outward passage of fluid from the cells, are the 

 following facts. There seems no close relation between 

 the degree of increased secretion and that of aggre- 

 gation. Thus a particle of sugar added to the secre- 

 tion round a gland causes a much greater increase of 

 secretion, and much less aggregation, than does a 

 particle of carbonate of ammonia given in the samo 

 manner. It does not appear probable that pure water 

 would cause much exosmose, and yet aggregation 

 often follows from an immersion in water of between 

 16 hrs. and 24 hrs., and always after from 24 hrs. to 

 48 hrs. Still less probable is it that water at a tempe- 

 rature of from 125'' to 130° Fahr. (51°-6 to 54°-4 Cent.) 

 should cause fluid to pass, not only from the glands, 

 but from all the cells of the tentacles down to their 

 bases, so quickly that aggregation is induced within 

 2 m. or 3 m. Another strong argument against 

 this view is, that, after complete aggregation, the 

 spheres and oval masses of protoplasm float about 

 in an abundant supply of thin colourless fluid; so 

 that at least the latter stages of the process cannot 

 be due to the want of fluid to hold the protoplasm 

 in solution. There . is still stronger evidence that 

 aggregation is independent of secretion ; for the pa- 

 pillcc, described in the first chapter, with which the 



