182 Dynamic Theory. 



utes, but the half of the turn growing from the light required nearty 

 four and a half hours, while the other half growing towards the light 

 was accomplished in less than one hour. 



Everyone has observed that solitary trees are more bushy, and put out 

 branches lower down their stocks than those growing in a forest, be- 

 cause the light has better access to their lower parts. 



It is a curious and significant fact that certain of the lower animal or- 

 ganisms possess chlorophyl. 



Semper raises the question whether these chlorophyl bodies may not 

 be separate organisms living with the little animals as commensals or 

 messmates, and yet not having anything to do with the vital economy 

 of the animal. It has been shown that in some, at least, of the animal 

 organisms the vortex viridis, for example the chlorophyl cells in- 

 crease and divide spontaneously, like other animal cells, zoospores, &c. 



If the chlorophyl cells act in the animal organism as they do in the 

 vegetable, they not only support themselves, but manufacture a large 

 surplus of starch which they do not need. It is extremely unlikely, in- 

 deed impossible, that the animal organism in contact with this starch, 

 in fact having it mingled with its own tissues, should not absorb and 

 make use of it. It is evidently one of those cases of reciprocation of 

 offices between mutually dependent organisms, which constitutes all 

 vegetable and animal organization above that of the single celled organ- 

 ism. In this case, probably the chlorophyl cell is formed from the 

 protoplasm of the animal by the action of light, just as it is formed 

 from the protoplasm of the plant. It then proceeds to digest carbonic 

 acid and form starch, the surplus of which goes to the support of its 

 animal host a clear case of a mutually profitable reciprocity. The 

 animal here is so close to the vegetable kingdom, that in fact both king- 

 doms are represented in the single organism. Throughout the animal 

 kingdom there is the same dependence on the chlorophyl cell for its 

 surplus products, and without them the animal kingdom could never 

 have come into existence. 



But the development of locomotive organs in the animal, making it 

 possible for him to go to the vegetable for his food, has rid him of the 

 necessity of retaining the chlorophyl cell in his own organization, and 

 so all animals, except some of the very lowest, have lost the chlorophyl- 

 lian function. In a primitive state of society, each family ground its 

 grist at home, but a division of labor enabled them to go to mill. 



Semper gives the following list of animals possessing chlorophyl, xanthophyl, &c. 

 Protozoa. Euglena yiridis. 

 Stentor viridis. 



Almost all Radiolaria. (Two families excepted.) 

 Spongilla viridis. 

 Cmlenterata. Hydra viridis. 

 Annuloida. Vortex yiridis, a Turbellarian worm. 



Also the decomposition of carbonic acid has been proved to be a function of the green 

 Turbellarian worm, Convolnta Schultzii. 



