this substance ($ 33) . The thickening and formation of 

 the walls of the vesicles and vessels Wolff considered the 

 result of the above mentioned movement of juices, which 

 gradually lose their volatility. As a result, the solid 

 substance is deposited in the walls of the extended rounded 

 cavities (vesicles) and canals (the future. vessels) . 

 Simultaneously, new vesicles and new rudiments of vessels 

 appear (§ 29). Wolff did not find any internal organization 

 in the vesicles constituting the organs of the plant, and 

 he objected against the fantasy of microscopists who 

 described non-existing structures. In the second remark 

 (to 5 38) he wrote: 



The extremely unreal substances , which Malpighi , 

 (Nehemiah) Grew, and (Anthony van) Leeuwenhoek 

 mentioned, are the fruits of their rich imaginations. 

 Thus, for example, they assumed that those vesicles 

 which I have described and interpreted are similar 

 to the glands of animals; vessels must enter them, 

 which because of their small size cannot be seen by 

 any microscope. These glands discharge their juice 

 in the vessels, which similarly occurs in the glands 

 of animals . Why do we imagine that which has no trace 

 in nature? Why, timidly, do we search everywhere for a 

 miracle? Maybe for the reason that the clever production 

 and wisdom of the Creator is revealed. It must not 

 be forgotten that the quality of the machine can be 

 judged, not by the number of its constituent parts, 

 but by the excellence and the simplicity of its result. 



The description of the emergence of the internal organiza- 

 tion of plants is considered an argument in favor of epigenesis 

 and against preformation. That same idea stands out in all 

 statements on the development of plants, including considera- 

 tion of the final formation of the leaves, formation of stem, 

 roots, flowers, fruits, and seeds. For example, the leaves, 

 which still do not possess their final form, finally become 

 formed, and in their place new young non-formed leaflets 

 originate. They are formed from the structureless substance 

 of the vegetational bud; that is why in the place of the 

 substance used for the formation of leaves, new structureless 

 substance appears (5 53) . 



In the second part of the dissertation there are factual 

 data and considerations concerning animal development. The 



52 



