1896.] MICROSCOPICAL JOURNAL 79 



their eggs in its ovaries^ which intention is frustrated by 

 the resistance of the ovary wall. 



A more curious instance still is that of the fertilisation 

 of the flower of the Yucca, a large liliaceous j)lant by a 

 small moth Yuccasella. This moth first lays some two 

 or three eggs in the ovary of a flower, and then, with a 

 special pretensile organ carried under its proboscis, 

 fetches some pollen from the anthers and plasters it on 

 the sticky stigma. The result is that the ovules are fer- 

 tilised and increase rapidly in size, serving as food for 

 the young larvsB. About twenty or more such ovules 

 will be devoured, but as about 200 will ripen in all it is 

 obvious that the plant is not by any means a loser by 

 this transaction, and that ensuring fertilisation with the 

 loss of a few ovules is better than risking the chances of 

 not being fertilised at all. 



Now let us turn for a moment from partnerships in 

 which plants are the chief or sleeping partners and ani- 

 mals are the working partners, to a few instances in 

 which the animal is chief partner, or practically the em- 

 ployer, giving to the plant protection, and perhaps also a 

 small amount of wages for work done. 



Most of you will know the fresh-water sponge, Spon- 

 gilla, or perhaps even more may have seen the fresh- 

 water polyp (Hydra viridis). Now both the fresh water 

 sponge and the fresh-water polyp are colored green, 

 not the same animal green color you find in the parrot's 

 feathers for instance, but a color of the same nature as 

 that which you find in trees and grass, and which has 

 been called chlorophyll or leaf-green. Now there is no 

 reason whatever why animals should not possess this 

 color, which is so useful to plants and enables them to 

 live, so to speak, on air, that is to assimilate the carbon 

 contained in the air ; but I will not here enter into a dis- 

 cussion on this point, nor dispute the right of Euglena, 



