114 THE SCOTTISH NATURALIST 



metamorphosis within the host, but has been swallowed in 

 drinking-water or with food. 



As regards the occurrence of Hairworms in the British 

 Isles, only the vaguest information is available. The gist of 

 the records of species and their distribution appears in Dr 

 Baird's Catalogue of the Species of Entozoa or Intestinal 

 Worms contained in the Collection of the British Museum^ 

 published so long ago as 1853. So far as Scotland is 

 concerned, the Catalogue contains definite references to 

 two species — " Gordius tolosanus" and " Goi'dius violaceus" — 

 both found in Berwickshire by Dr George Johnston. No 

 definite localities are given for the occurrence of " Gordius 

 aquatictis" Regarding the use of this last name a word of 

 warning may be given. It is inevitable that a creature so 

 common as the Hairworm should frequently be brought to 

 experienced naturalists for baptism, and hitherto it has been 

 almost as inevitable that the creature so brought should be 

 dubbed Gordius aqjiaticus. My own experience, however — 

 and I have examined specimens from parts of Scotland 

 ranging from the English border to Shetland — is that even if 

 the Gordius aquaticus of Linnaeus is specifically recognisable 

 to-day (and by some competent authorities it is held to be 

 unrecognisable), then it is certainly not the " Common " 

 Hairworm of our ponds and ditches. 



The adult Hairworm is the only stage that is likely to 

 come under the notice of the general collector. It is very 

 long and slender, generally of a dark brown, or in young or 

 female specimens of a honey-yellow colour. The body is 

 cylindrical and exceedingly tough, but in autumn after the 

 extrusion of the eggs the walls seem to collapse and the body 

 becomes flattened and twisted. The head end in all adults 

 is simply indicated by a tapering away of the body to a point 

 more or less rounded. The tip of this conical head is much 

 paler in colour than the general body-tint, and great use is 

 made of it in the process of locomotion, during which it 

 may be closely applied to the stems of water-weeds or to 

 the walls of the glass vessel in which the creature is a captive. 

 The head is thus anchored, and becomes a pivot round which 

 the body moves. Many little tests were made to prove the 



