Attempt to Subordinate I'rotixta to Cell-Theory 287 



limitation to that application which lit- believes necessary. 

 "One must ever he-sit ate- to consider the fully developed In- 

 fusoria as unicellular organisms, for they arc not merely 

 cells that have undergone further simple growth, but the 

 original cell structure has given place to an essentially dif- 

 ferent organization which is entirely foreign to cells." 7 That 

 is, the cell conception applies to these animals, according to 

 Stein, only when they are in the earliest or germinal stages 

 of their lives. This view is brought out still more clearly 

 by the following comparison which he makes between the 

 individual development of a unicellular and a multicellular 

 organism. "The germinal spheres or embryonal cells of 

 the Infusoria do not behave at all like the egg cells of the 

 higher animals. By a process of fission [these latter] break 

 up (zerfallen) into an aggregate of smaller embryonal 

 bodies, the constituting cells (the germinal spheres of the 

 Infusoria), which transform themselves just as they are 

 into the embryonic body sarcode, the kernel [Aww] becom- 

 ing the nucleus, of the young Infusorian. The embryo of 

 the Infusorian is therefore in the strictest sense of the word 

 a unicellular organism." In this sense, and in this sense 

 only, Stein goes on to say, he subscribes to the doctrine that 

 the Infusoria are unicellular. Stein's conception of the 

 adult Infusorian as contrasted with the embryonic Infusor- 

 ian was probably influenced by his having mistaken an 

 Ascinetan, parasitic in certain ciliates, for embryos of the 

 hosts, and on this error he based his theory that these 

 eiliates pass through an ascinetan stage in their ontogeny. 

 But this error does not invalidate his statement of the funda- 

 mental difference between unicellular and multicellular or- 

 ganisms as to the sort of transformation undergone in their 

 individual development. Wherever sporulation occurs, 

 growth of the spores into the adults would exemplify Stein's 

 main point, and this point is of capital importance as we 

 shall contend more at length later. 



