OBSEKVATIONS ON EARTHWORMS 



41 



Finally, it may be mentioned for the benefit of those who are 

 already acquainted with the structure of the earthworm, that the 

 method by which the curious parasitic gregarine gets into the worm 

 is still unknown. Is there an intermediate host ? The clearing up 

 of this interesting point would doubtless take a long time. It is for 

 this reason probably that a not difficult piece of research has been 

 left alone, though it is one which would well repay the trouble 

 spent on it by bringing to light a process which has long baffled the 

 theories of zoologists. 



Only one or two naturalists have turned their attention to 

 British earthworms, some of which, as they live under the bark of 

 dead trees, are called tree worms ; and there still remains much to 

 be found out with regard to their number and distribution. 



FIGURE 169. An Earthworm. 



