POLYGASTRIA. 25 



given by the great naturalist just mentioned, afford most satisfactory 

 examples of a pellucid globule, dividing and subdividing like the 

 hyaline in cells. 



*' In many other of Ehrenberg's figures of the Polygastric Infusoria, 

 the corresponding part appears to me to be denoted by a blue, red, or 

 green colour, according as there had been added either indigo, carmine, 

 or sap-green. This accords with what has been mentioned in a former 

 page, regarding cells, namely, that a foreign substance becomes added 

 and assimilated through the hyaline. 



" Fecundation of the ovum takes place in the same manner as nutri- 

 tion of the cell, and seems, in some instances at least, comparable to 

 the nutrition of one of the Infusoria. 



" But farther, I recognise in Ehrenberg's delineations of the In- 

 fusoria, not merely a cell-formation, but everywhere the existence of 

 transitory or assimilative cells. 



"^ And farther still : the infusorial cells, like the cells of the larger 

 organisms, have their origin in globules which become discs or " cyto- 

 blasts ; " these passing through stages such as those of ordinary cells. 

 Thus in Ehrenberg's Monadina are to be found, I think, the following 

 grades, perfectly analogous to the grades of cells : — 



" 1. Globules and discs. 



" 2. Discs with a pellucid point. 



" 3. The point dividing. 



" 4. Nucleated cells. 



" 5. The nuclei dividing and thus giving origin to 



" 6. Young cells, which are seen both within and escaped from 

 parent cells. 



" There really seems to have been much truth in the remark long 

 since made by Oken, that animals are groups of bodies comparable to 

 the Infusoria. The cell is itself a little organism ; and cells coalesce 

 to form a larger one. 



" The remarks just made respecting fissiparous generation, 1 appre- 

 hend, may be applied to gemmiparous reproduction, or propagation by 

 means of buds." 



No doubt the minute Infusoria, which seem to have their develop- 

 ment arrested at the first or nearest stage from the primitive cell- 

 formation, offer close and striking analogies to the primitive cells 

 out of which the higher animals and all their tissues are developed ; 

 but the very step which the Infusoria take beyond the primitive cell- 

 stage invests them with a specific character as independent and dis^ 

 tinct in its nature as that of the highest and most complicated 

 organisms. No mere organic cell, destined for ulterior changes in 

 a living organisation, has a mouth armed with teeth, or provided with 



