December 15, 1911] 



SCIENCE 



845 



A light ball of pith or cork or a ping-pong 

 ball covered with varnish and rolled in fine 

 sawdust is placed in a round pasteboard mail- 

 ing tube and thrown by a quick motion of the 

 tube as indicated in the accompanying sketch. 

 The ball rolls along one side of the tube and 

 is spinning rapidly when it leaves the end of 

 the tube. The result is that the ball curves 

 sharply upwards as it flies through the air, in 

 some cases describing the cusped curve which 

 is mentioned by Professor J. J. Thomson. 

 W. S. Franklin 



SEED DISTRIBUTION BY SURFACE TENSION 



In response to Mr. Becker's suggestion in 

 Science, November 17, I may record what I 

 have been accustomed to state in public con- 

 cerning the distribution of seeds of water lilies 

 (Nymphcea (L.) Sm.). Indeed, I was sur- 

 prised to find that the observation had not 

 already been published. 



The fruits of Nymphceas mature under 

 water, and burst irregularly, discharging the 

 seeds a few inches or feet below the water 

 surface. But the seeds rise at once and float 

 by reason of a buoyant aril. The aril forms 

 a kind of double-walled sac, open at one end, 

 and enclosing the seed. It is mucilaginous in 

 character and carries little bubbles in and 

 upon it. I have often watched a mass of such 

 seeds of N. odorata, N. cmrulea or N. lotus 

 upon a water surface. They separate from 

 one another spontaneously and distribute 

 themselves over the tank or pond in all direc- 

 tions, even though both water and atmosphere 

 be perfectly still. It is wonderful how they 

 steer about among floating leaves, and travel 

 to the confines of their basin. Each one seems 

 to repel all others. I have always believed this 

 was due to surface tension or diffusion effects, 

 but have never undertaken to prove the point 

 or to determine the substances causing it. 

 After some hours, the aril splits, the pieces 

 curl up, and the heavy seed is released and 

 sinks to the bottom of the pond. 



Henry S. Conard 



Geinnell College, 

 Grinnell, Iowa, 

 November 20, 1911 



■ models of VORTIOELLA and CYCLOPS 



To THE Editor of Science : The Department 

 of Animal Biology of the University of Minne- 

 sota recently received a model of a small 

 colony of Vorticella and a model of Cyclops 

 that deserve public notice. 



These models are advertised in reputable 

 catalogs and the stands bear printed labels that 

 announce : 



Awarded Gold Medal, Franco -British Exhibition, 



1908 



Biological Models. Made by Smedley, London, S. E. 



Sole Agents, Gallenkanip & Co., 19 and 21 Sun St., 



Finsbury Square, London, E. C. 



The models are made of a soft paraffin and 

 are, without qualification, the poorest models 

 that I have ever known to be advertised and 

 for sale. They are absolutely devoid of any 

 scientific value and are grossly untrue to even 

 the most evident structural features. The ap- 

 pendages of the Cyclops (sp. ?) are uniramous 

 and no attempt has been made to indicate the 

 relative lengths of the joints. Even the num- 

 ber of joints differs in the members of a pair. 

 There is no attempt to represent the vestibule 

 or " disk " of the Vorticella and the cilia are 

 represented by feathers pressed into the par- 

 affin. The paraffin is very slovenly put over 

 wires and everything about the models indi- 

 cates very crude workmanship and lack of 

 knowledge. And such things are awarded gold 

 medals ! 



This is submitted for the protection of those 

 disposed to use models in the class room and 

 the laboratory. 



Henry F. Nachtrieb 



siphon springs and sink holes 

 Siphon Springs. — Intermittent springs as 

 the result of the combination of a reservoir 

 and siphon have long been favorite illustra- 

 tions in the standard text-books of physics to 

 show the practical application of the siphon. 

 The familiar figure shows a small hill with a 

 large cavern discharging its water by means 

 of a siphon. Such a cavern emptying into a 

 valley in this way must be extremely rare in 



