112 THE SCOTTISH NATURALIST 



brought home amongst the roots of marsh plants in Aber- 

 deenshire. Further, they generally occur either singly, 

 twisted around the stems and leaves of water-weeds, or in 

 groups entangled in an apparently inextricable knot. So it 

 is that their appearance, supported by their habit, suggests a 

 resemblance less to an animate worm than to a length of 

 brown whipcord, a piece of violin string, or a horse-hair. In 

 country districts, where they are known to every schoolboy, 

 the last likeness is most frequently recognised, and the old 

 tale of a horse's hair which, having been immersed in water, 

 has sprung to life as a Hairworm, is still preferred (and 

 occasionally insisted on) as the explanation of their origin, 

 in place of the real miracle of the Hairworm's birth. 



The salient facts regarding the curious life-history 

 through which the creature passes before reaching adult 

 life are well worth repeating. There are, according to 

 Camerano, four stages — i. TJie cinbryonic stage in a strict 

 sense, including the segmentation and gastrulation of 

 the egg. 2. Tlie larval stage : a minute worm-like larva, 

 with a proboscis armed with bristles and hooks and a 

 boring apparatus. 3. T/ie juvenile stage, when the thread- 

 like body of the adult has been assumed but the sexual 

 organs are still incompletely developed and the surface 

 markings have not altogether assumed adult characters. 

 4. The adult stage, with filiform body and sexual organs 

 completely developed and functional. 



It is apparent from the different attributes of these 

 stages that their modes of life differ. The eggs are fertilised 

 within the female, and are laid in long strings upon water- 

 weeds from April to August. Within an egg a larva 

 develops, finally bursting through the egg-membrane and 

 swimming in the water or crawling on the bottom until an 

 insect larva comes within reach. Into this host, generally 

 the young of a midge, the larva penetrates by means of its 

 boring apparatus, entering either through the skin or through 

 the wall of the alimentary tract, and coming to rest most 

 often in a muscle. Here it remains throughout the winter, 

 being retained during the development of the aquatic larva, 

 so that in spring it passes into the adult insect. This 



