752 SUMMAEY OF CTJREENT RESEARCHES RELATING TO 



ment of those actions termed organic or vital, it is of importance to 

 know to what degree the anatomical and physiological complexity of 

 the independent beings called unicellular may be carried ; that is, of 

 those independent organisms which are incontestably the homologues 

 of the anatomical units of compound living bodies. It is also import- 

 ant to know whether a unicellular animal or vegetable of independent 

 habit of life is to have one additional elementary part or several — 

 unlike, though homologous — added to it by that process of gradual 

 structural complication which is the result of its development ; 

 whether, that is to say, this being, which has the structure of a fer- 

 tilized ovum, imitates its development also by leaving the cytode, or 

 unicellular stage, for that of a multicellular organism, composed of 

 dissimilar cells, which only reproduces the original unicellular form 

 at a later period. 



Now, there is a fact in the history of the acinetine form PodopJirya 

 which is also observable in all other unicellular animals and plants. 

 It is that during those phases of its reproduction in which the pro- 

 duction of gemmee causes them temporarily to pass through the multi- 

 cellular stage, each gemma, or cell, already represents a new indepen- 

 dent individual. It does not represent a constituent part associated 

 with other parts to make up a new multicellular organism, which, in 

 this condition, with or without increase of structural complication — 

 that is, with or without the aildition of anatomical units, and new organs, 

 combining to perform in harmony certain actions — undergoes further 

 evolution. The multicellular condition by no means represents the 

 transition from one degree of organization to a superior one, but only 

 a temporary addition to an individual of other individualities, which 

 are already distinct from each other, and which are continually less 

 and less forming part of the organism from which they are derived, 

 instead of the opposite being the case, as in growth, properly so 

 called. 



Thus the body of Podophrya does not represent an ovum any more 

 than does that of the other unicellular organisms. The Infusorian is 

 a plant or an animal, as the case may be ; but it is neither an oophyte 

 nor an oozoon, nor, above all, indifferently either the one or the other 

 according to the media in which it is placed. Besides, independently 

 of its peculiarities of structure, and often of the reactions which allow 

 us to distinguish the ovum, whether animal or vegetable, from a pro- 

 tozoan or protophyte, it must be noted that no ovum enguli)hs foreign 

 particles in order to digest them, and to further its own development, 

 as do so many Infusoria. 



The structural complexity of the unicellular animals may in 

 such forms as the Noctilucae and the Infusoria, go the length of pro- 

 ducing a tentacle and a flagellum, a true mouth-opening, with more or 

 less elaborate lips, &c. In a number of Inlusoria, both ciliated, 

 acinetine, and flagellated, besides the cilia of the one, the radii or 

 suckers of the second, the flagellum of the last, and the pulsatile 

 vesicle which is wanting in the adult Noctiluca), there may occur a 

 more or less complicated shell and peduncle. In these last we have 

 so many genuine organs, fulfilling uses which are very distinct from 



