468 PROTOPLASM 



water in comparison with the high vahie ordinarily existing 

 between a true fat and water. The number of molecules of 

 lecithin in contact with water at the surface tends to increase 

 because of low interfacial tension, and the surface of the lecithin 

 advances into the water; myelin forms result. It is likely that 

 many superficial protoplasmic processes arise in the same way. 

 F. Weber has described myelin forms from the chloroplasts of 

 Spirogyra when put into a soap (sodium oleate) solution. Proto- 

 plasmic processes (similar to those in Fig. 173) were first described 

 by Fol as coming from the surface of ripe echinoderm eggs. 

 These may serve to attract or guide sperm. Bacteria and many 

 types of one-celled organisms develop delicate protoplasmic 

 protrusions {e.g., cilia) which are functional; these processes may, 

 however, be of protoplasm and not of lipoid alone. 



