226 EVENINGS AT THE MICROSCOPE 



adult and final stage, they have passed by metamorphosis 

 through conditions of life in which they were active rov- 

 ing little creatures, endowed with the power of swimming 

 freely in the wide sea. In this condition they present the 

 closest resemblance to familiar forms of Crustacea, as you 

 will perceive when you examine some specimens of the 

 larvae that I am able to show you. 



I have in one of my tanks an individual of the fine and 

 large Barnacle, Balanus porcatus, which for several days 

 past has been at intervals throwing out from the orifice of 

 its shell dense clouds of atoms, which form compact col- 

 umns reaching from the animal to the surface of the water. 

 One of these cloudy columns, when examined with a lens, 

 is seen to be composed of thousands of dancing creatures 

 resembling the Water-fleas that we. lately examined. They 

 maintain a vivacious motion, and yet at the same time 

 keep their association and the general form of the column. 



Taking out a few of the dancing atoms, and isolating 

 them in this glass stage-cell, we see that they have exactly 

 the figure, appearance, and character of the young of the 

 common Cyclops, so that you would, without hesitation, if 

 you knew nothing of their parentage, assign them to that 

 well-known genus. Their movements are almost incessant, 

 a series of jerking progressions performed by quick but 

 apparently laborious flappings of the limbs, right and left 

 together. They occasionally rest from their exertions for 

 a few moments, but seem to have no power of alighting 

 on any object. 



But in order to obtain a more precise idea of the 

 structure of this tiny creature, we must manage to re- 

 strain its liberty a little, by applying gentle pressure with 

 the compressorium, just sufficient to confine it without 



