1893.] NEW-YORK MICROSCOPICAL SOCIETY. 107 



Actinocychis, Coscinodiscus, and Biddulphia Icevis, which appear 

 to pass their life cycle attached to water plants. But we also 

 know that millions of the travelling frustules are removed from 

 water plants which, when dried, exhibit the frustules in illimit- 

 able numbers, as may readily be determined from the mass of 

 moss-like water plants sent herewith to the Society for distribution 

 to such members as may desire to study them in the dry state. 



Now, I would suggest that the character of the subjective 

 motion of the protoplasm of the diatom possibly has its homo- 

 logue in the cilia, pseudopodia, and other admitted protoplasmic 

 appendages of the true Infusoria, and the Rhizopoda, and, in fact, 

 the Protozoa generally; that is to say, in a contractile and ex- 

 tensile power common to the lowest forms of microscopic ani- 

 mal life. Since the activity of the protoplasmic sheath of the 

 Amphiprora ornata is now clearly pointed out, it is within the 

 range of verification by the simplest means. One is certain of 

 witnessing a phenomenon that has for many years been of mys- 

 terious interest to observers. But there are two kinds of proto- 

 plasm, that of plants and that of animals. And the simplest in 

 structure of the animal protoplasms is that associated with the 

 Rhizopoda, which, barring the nucleus, are structureless, gelatinous 

 masses, having an inherent extensile and retractile power, and 

 presenting various modifications of outline. When employed in 

 seeking their food, then their characteristics are best shown and 

 appreciated. 



Amosba proteiis offers us protoplasm in one of its simplest con- 

 ditions, that is, where it is devoid of the power of secreting a 

 mineral covering, or even the rudiments of an internal skeleton. 

 From this simple stage protoplasm passes through rising grades 

 of complexity, ending in its power sometimes to secrete a chitin- 

 ous covering, and sometimes a silicious shell or a shell built up 

 of grains of silex. There is also the simple, structureless proto- 

 plasm of the Foraminifera, which is endowed with the power of 

 secreting a shell from calcareous sources, and that of the sponge, 

 which exercises the power of assimilating the molecules of car- 

 bonate of calcium or silica disseminated in the fluids of its 

 habitat. 



To further expand the relation between animal protoplasm and 

 its peculiar power to secrete silica, I will offer my illustrations 



