118 Dr Barry on the Unity of Structure 



must be continually changing, can exist, indeed, at no two pe- 

 riods of time ; inasmuch as new elements are continually enter- 

 ing into its constitution, while old ones are departing. But the 

 same separate or distinct existence the same individuality 

 continues.* 



A law, not less vast in its importance, than it seems to be ge- 

 neral in its application, may be supposed to direct structure in 

 the animal kingdom. This law requires that a heterogeneous 

 or special structure, shall arise only out of one more homoge- 

 neous or general; and this by a gradual change. The import- 

 ance of this law appears to have been insisted on chiefly by Von 

 Bar, who arrived at it by long and attentive observation of 

 development. 



Let us then inquire, in the first place, what analogy there is 

 in the states of germs in general, at the earliest period of obser- 

 vation ; and whether thev have in common, a homogeneous or 

 general structure. 



In animals presenting the most simple manifestations of life, 

 c< in which, every point of the creature is, as it were, an epi- 

 tome of the whole, without any relation to, or dependence on, 

 the rest ; and capable, therefore, when separated from the rest, of 

 an independent existence,"-)- maturity alone appears sufficient 

 to produce offspring, and simple separation sufficient to consti- 

 tute a new being. Such is the case with many zoophytes. 



Reproduction becomes less simple, as vitality grows complex ; 

 because now, " each point of the creature has a more close rela- 

 tion to, and dependence on, the rest, than before.^ When 

 something like ova begin to be discernible, they consist of a 

 half-fluid, throughout homogeneous, more or less granulous 

 mass. This is the state of bodies regarded as ova, in some In- 

 fusoria, some Polypes, and many other Zoophytes. Bodies of this 

 kind have been called " Germinal Granules."" Such imperfect ova 



* Cessation of the changes spoken of, constitutes death. The state of be- 

 ing subsequently, forms a subject, of which it would here be out of place to 

 treat. It is sufficient that revelation makes us acquainted with the fact, that 

 human existences continue, after they have ceased to be represented by com- 

 binations of elements, performing functions, the sum of which is called life. 



f Dick, in the Trans, of Prov. Med. and Surg. Assoc., vol. iv. p. 344. 



$ Dick t 1. c. p. 344. 



