96 EDWARD POTTS : 



use through the opening in the stage. A series of solid 

 blocks must now raise the eye piece to the level of the eye of 

 the observer, and another " Eiffel tower" must be built up, 

 on which the particular jar wanted must stand, and must be 

 laboriously adjusted with blocks and books to suit the exact 

 height of the selected atom that is to be examined. 



THE EARLY MOVEMENTS OF. THE LARVA BEFORE ATTACHMENT 



My recent journal reads: "July 3rd, 1907. The micro- 

 scope was last evening directed toward a bicapitate micro- 

 hydra, and we were surprised to find this morning in close 

 proximity with it, a larva that had undoubtedly been liberated 

 at some time during the night, although no hint of it had 

 been noticed the evening before. As there was now no inter- 

 fering debris I watched this larva for a long time with the 

 highest powers I could use, trying to discern its mode of 

 motion, but without success. Yet it was easy to see that it 

 had moved, and that with considerable speed, in a compara- 

 tive sense, as was shown when an eyepiece micrometer was 

 used. The minor divisions of the scale were passed much 

 faster than I had expected, and while I did not succeed in 

 determining any certain line of progress, the changing curva- 

 tures of its extremities convej^ed the impression that it was 

 following a simple wave line, controlled by a very deliberate 

 bending of one end and then the other, that had an effect like 

 that of pseiidopodia in dragging or pushing the only half 

 animate body in some %vay to some ivhere. Certainl}- there 

 were no cilia, flagella or other external organs, and the sup- 

 porting surface of the glass was never abandoned." 



The time during which they remain in this immature, 

 larv^al condition is quite uncertain. I have generally placed 

 it between one and two weeks, having made many efforts to 

 determine this, with its several points, by stenciling their 

 positions upon the sides of my jars and measuring the dis- 

 tances moved during definite periods, but have failed to dis- 

 cover any certain rule or fact except that they do move out of 



