THE GAPE- WORM. 79 



gested have been : — (1) The Bird-Lice (Mallo- 

 pliaga), (2) various Mollusca, and (3) Earthworms. 



(1) The supposed connection hetween Lice and 

 Gapes. — This theory, for we must call it such, is 

 based upon three points, namely: — (1) Dr. Cob- 

 bold's suggestion (p. 77). (2) The observations of a 

 Mr. Halsted, who noticed that if he cleaned off 

 certain insects (what they were we are not told!) 

 which were observed attached to the head of some of 

 his chickens, that those broods never had Gapes, but 

 those upon which the insects remained suffered from 

 the disease. These i certain insects ' were probably 

 lice ; he therefore at once assumed that there was 

 a connection between Gapes and the insects he 

 observed. But Mr. Halsted says of this insect that 

 "it is not a louse." The figure in Mr. Wright's 

 excellent book on Poultry is, however, one of the 

 Mallophaga, but what species it is not possible to 

 tell. (3) Thirdly, inferences have been drawn from 

 other parasitic worms, such as the Taenia found in 

 the do^\ ^vhich is derived from the cvstic stage 

 found in the dog's louse {Tricliodectes latits). Un- 

 doubtedly, we often find lice when Gape-worms 

 are present, because, unfortunately, very many 

 fowls suffer from this insect infestation recorded in 

 one of the previous articles. On the other hand, 

 I have numerous records of Fowls in isolated runs 

 which were quite free from lice and yet suffering 

 from Gapes. Again, we must remember that the 

 Nematode worms are not Cestode worms. Many of 



