6 RESEARCHES ON FUNGI 



so often made in mycological laboratories, it is during the swarming 

 time that the larvae of Strongylus species find their way on to 

 Pilobolus fruit-bodies, up bits of straw, the tips of which they often 

 cover, and up the sides of the dish upon which, when very numerous, 

 they may arrange themselves so as to form a curious retiform 

 pattern (Fig. 4). Persoon, Tode, Grove, the writer, and many 

 others have seen one or more of the little worms wriggling about in 

 drops or films of moisture on the exterior of a subsporangial swelling ; 



Fig. 3. — Strongylus larvae (Nematode worms) which swarmed up the side of a 

 glass culture-dish from horse dung, about seven days after the dung 

 (fresh) was placed in the dish (c/. Fig. 4). They were separated from one 

 another by immersing them in water on a slide, where they wriggled 

 violently. With the addition of iodine, they came to rest, straightened, 

 died, and took on a yellow colour, whereupon they were photographed. 

 Magnification, 51. 



but, hitherto, mycologists may not have realised that the worms are 

 but larvae and that, when climbing on to a Pilobolus or up the side 

 of a dish, they are only following a swarming instinct which, when 

 it leads them under natural conditions to ascend grass-blades, gives 

 them a chance to be swallowed by a horse and thus to enter an 

 animal in which they may continue their development.^ When a 

 Pilobolus fruit-body explodes, any Strongylus larvae which may 

 be present on the sporangiophore must be thrown down violently on 

 to the surface of the dung, while, if a larva should happen to be on 

 the sporangium, it will be carried away with the projectile. 0. F. 



^ For the facts concerning the life-history of the Roundworms of the horse, I am 

 indebted to Dr. G. Hadwen of the Ontario National Research Foundation. 



