HISTORY OF PILOBOLUS 5 



worm has been repeated in recent years by Boudier ^ who, in one of 

 the Plates of his splendid Icones Mycologicae (1905-1910), illustrates 

 Pilobohis Kleinii in colours and shows us two worms in the middle 

 of a subsporangial swelling enlarged twenty-five times (Fig. 2). 

 The worms look as though they might have been on the exterior of 

 the under side of the swelling, but that Boudier intended us to 

 think that they were inside the great vacuole is shown by his 

 description of the drawing : " Autre adulte, on remarque dans la 

 vesicule superieure 2 anguillules qui s'y sont introduites." A priori 

 it seems most unhkely that two worms should succeed in penetrating 

 into a sporangiophore without injuring or killing it or leaving any 

 trace of their mode of entrance ; and, in view of the critical observa- 

 tions of Tode, Persoon, Currey, and Coemans, already cited, it must 

 be concluded that Boudier, like Miiller one hundred and thirty years 

 earlier, was the victim of an optical illusion. 



When a fruit-body of a Pilobolus has been removed from its 

 substratum and has been placed horizontally on a glass slide, any 

 worm which may be in the film of moisture where the subsporangial 

 swelling is in contact with the slide is magnified by the swelling 

 which acts as a lens. It may well be that this optical effect originally 

 suggested the idea that a AVTiggling worm, which in reality is on the 

 exterior of the swelling, seems to be moving about inside. 



Miiller's worm was probably a larval Roundworm (one of the 

 Nematoda) and, if it was, it may have belonged to a species of the 

 genus Strongylus. There are several species of Strongylus, e.g. 

 S. vulgaris, which are parasites of horses. They deposit their eggs 

 in great numbers in the caecum and colon of the alimentary canal of 

 the horses concerned, and the eggs pass to the exterior in the faeces. 

 After a mass of dung has been dropped upon the ground, the eggs 

 hatch within twenty-four hours and, after seven days, the larvae 

 (Fig. 3), which have fed on the faecal matter, begin to swarm on to 

 grass blades, etc., where they pass through a few moults and are in 

 a favourable position to be swallowed by grazing horses. Within 

 these animals they grow to a length of two inches or more and become 

 sexually mature. In unsterilised horse-dung cultures, such as are 



1 E. Boudier, Icones Mycologicae on Icoiiographie dcs Cliampignons dc France 

 principedcmcnt Discomycetcs, Paris, 1905-191U, PI. 582, e. 



