ELEMENTARY MORPHOGENESIS 49 



von Baer, most clearly appreciated these analytical differences 

 between animal and vegetable morphogenesis. They become 

 a little less marked if we remember that plants, in a 

 certain respect, are not simple individuals but colonies, and 

 that among the corals, hydroids, bryozoa, and ascidia, we 

 find analogies to plants in the animal kingdom ; but never- 

 theless the differences we have stated are not extinguished 

 by such reasoning. It seems almost wholly due to the 

 occurrence of so many foldings and bendings and migrations 

 of cells and complexes of cells in animal morphogenesis, that 

 an earlier stage of their development seems lost in the later 

 one ; those processes are almost entirely wanting in plants, 

 even if we study their very first ontogenetic stages. If we 

 say that almost all production of surfaces goes on outside 

 in plants, inside in animals, we shall have adequately 

 described the difference. And this feature again leads to 

 the further diversity between animals and plants which is 

 best expressed by calling the former " closed," the latter 

 " open " forms : animals reach a point where they are 

 finished, plants never are finished, at least in most cases. 



I hope you will allow that I have tried to draw from 

 descriptive and comparative embryology as many general 

 analytical results as are possibly to be obtained. It is not 

 my fault if there are not any more, nor is it my fault if the 

 results reached are not of the most satisfactory character. 

 You may say that these results perhaps enable you to see a 

 little more clearly and markedly than before a few of the 

 characters of development, but that you have not really 

 learnt anything new. Your disappointment my own 

 disappointment in our analysis is due to the use of pure 

 description and comparison as scientific methods. 



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