V] 



THE SHAPE O'F A SPLASH 



391 



cup and the annulation of the stem are phenomena of the same order. 

 A cord-hke thickening of the edge of the cup is a variant of the 

 same order of phenomena; it is due to the checking at the rim of 

 the flow of hquid from below, and a similar thickening is to be seen, 

 not only in some hydroid calycles but also in many Vorticellae 

 (cf. Fig. 124) and other cup-shaped organisms. And these are by 

 no means the only manifestations of surface-tension in a splash 

 which shew resemblances and analogies to organic form*. 



The phenomena of an ordinary liquid splash are so swiftly tran- 

 sitory that their study is only rendered possible by photography: 



01 [VA~/"'^^^VY 



Fig. 117. Calycles of Campanularia spp. 



but this excessive rapidity is not an essential part of the pheno- 

 menon. For instance, we can repeat and demonstrate many of the 

 simpler phenomena, in a permanent or quasi-permanent form, by 

 splashing water on to a surface of dry sandf, or by firing a bullet 

 into a soft metal target. There is nothing, then, to prevent a slow 

 and lasting manifestation, in a viscous medium such as a proto- 

 plasmic organism, of phenomena which appear and disappear with 



* The. same phenomena are modified in various ways, and the drops are given 

 off much more freely, when the splash takes place in an electric field — all owing 

 to the general instability of an electrified liquid -surface; and a study of this aspect 

 of the subject might suggest yet more analogies with organic form. Cf. J. Zeleny, 

 Phys. Rev. x, 1917; J. P. Gott, Proc. Cambridge Philos. Soc. xxxi, 1935; etc. 



t We find now and then in certain brick-clays of glacial origin, hard, quoit- 

 shaped rings, each with an equally indurated, round or flattened ball resting on it. 

 These may be precisely imitated by splashing large drops of water on a smooth 

 surface of fine dry sand. The ring corresponds, apparently, to the crater of the 

 splash, and the ball (or its water content) to the pillar rising in the middle. 



