84 CHARACE^. 



surface of the membrane, their destination might be con- 

 jectured. The delicate and tender membrane itself might 

 be regarded as the matrix for the developement of these 

 granules, which, when mature quit it, and join the other 

 granular bodies contained in the circulating fluid, and the 

 nature of which is itself probably determined by their pre- 

 sence. That the granules studding the inner membrane do 

 in some way or other enter the circulating fluid, is rendered 

 highly probable by the fact that the majority of particles 

 which it contains bear a close resemblance to these granules. 

 Mr. Yarley further remarks in reference to these granules, 

 that if any of them, situated in the middle part of a cur- 

 rent, be disturbed by injury, no effect is produced, the 

 stream passing on as before; but that if they be displaced 

 over the boundary lines, a communication takes place be- 

 tween the two currents ; a portion of the fluid near the 

 boundary line, instead of passing on to the end of the cells, 

 crosses over it into the returning current, and passes on 

 with it, a portion of the descending, in like manner, joining 

 the ascending and following its course. " I believe," says 

 Mr. Varley, " that in this case the fine membrane ' is not 

 wounded, but is probably loosened from its adhesion to the 

 ridge, the green vesicles only being removed or injured: 

 but it shows that there is a most intimate connexion be- 

 tween these vesicles and the circulation ; and they appear to 

 govern the circulation ; for in the case above stated, where a 

 clear space was refilled with green vesicles anastomosing 

 had taken place ; but when the spot was again coated with 

 vesicles, the anastomosing also ceased, the fluid having 

 again taken its direct course, coinciding correctly with the 

 track marked out by their arrangement. I am led to think 

 that any wound of the membrane would kill that whole cell, 

 by submerging the vesicles in the thick or the inner fluid, and 

 thus cutting off the continuity of their action, or by the 

 different fluids mixing and so destroying their action. The 

 fine membrane with the vesicles is seldom removed far 

 enough from the tube to shew the colourless space between 



