268 THE ZOOLOGIST. 



VARIATION (AS ILLUSTRATED BY A DOUBLE- 

 HEADED WORM). 



By H. Victoe Jones, 



Assistant Demonstrator in Zoology, Bangor University College, North Wales. 



Duking the summer of 1912, while examining a number of 

 earthworms of the species Lumbricus, which had been brought 

 to the laboratory by Mr. J. A. Baxter, of Llanfairfechan, for the 

 purpose of dissection, I was fortunate enough to come across a 

 specimen of Lumbricus which showed marked Meristematic 

 Variation, commonly known as a Double-headed Worm. A 

 second worm was also discovered, showing incipient bifurcation. 

 Both worms were sexually mature, and in very good condition 

 when obtained. 



A close observation was kept on the habits and instincts of 

 these creatures, for the purpose of finding out whether they be- 

 haved differently from normal individuals of the same species. 

 They were under observation for a period of eight weeks, during 

 which time they were in a thriving condition. From the character 

 of their Variation many interesting facts were obtained. 



At the end of the series of experiments, under the control and 

 supervision of Professor P. J. White, the worms were killed, and 

 will at some future time be examined anatomically, as it will be 

 interesting to follow the Variation in the internal structures of 

 the alimentary and nervous systems respectively. 



Before giving a very brief account, morphologically and 

 physiologically, of these worms, it would be advisable to give 

 here a summary of the extent of the knowledge and importance 

 of Variation. 



Bateson, in his ' Materials for the Study of Variation,' 1894, 

 gives a very clear and concise explanation of the subject : " To 

 solve the problem of the forms of living things is the aim of the 

 present-day naturalists." He asks : " How have living things 



