io6 



RESEARCHES ON FUNGI 



mirror of the microscope and the image of its shadow as produced 

 on the wall of the upper side of the subsporangial swelling was then 

 focussed with the low power (ocular No. 10, objective No. 16 with 

 the end-lens removed, Bausch and Lomb system). The exposure 

 of the plate was for twenty seconds and the magnification of the 

 fruit-body on the plate was forty diameters. In the photomicro- 

 graph the oval spot of hght and the image of the shadow of four 

 fingers and part of the thumb of the hand, which could be seen 



with the eye on the upper wall of the subspor- 

 angial swelhng, are clearly visible. 



In Fig. 52 is shown a photograph of a white 

 card bearing a black printed letter A. The card 

 was 4-1 cm. long and 3-5 cm. wide, and the 

 letter A was 2-5 cm. long. The condenser and 

 the mirror were removed from the microscope 

 and the card was placed on the dark table within 

 the horse-shoe base of the microscope, so that it 

 was visible when the eye looked down the micro- 

 scope tube. The card was illuminated by direct 

 sunlight. The fruit-body, as before, was con- 

 tained in a compressor cell set on the stage of 

 the microscope. The exposure of the plate was 

 for a few seconds and the magnification of the 

 fruit-body on the plate was about thirty diameters 

 (ocular No. 5, objective No. 16 with the end-lens 

 removed, Bausch and Lomb system). In the photomicrograph the 

 image of the card with its letter A, which could be seen with the 

 eye on the upper wall of the subsporangial swelhng, is clearly 

 visible ; and, again, we have conclusive evidence that the sub- 

 sporangial swelling can act like a lens. 



Although, hke other more or less globular lenses, the subspor- 

 angial swelhng of Pilobolus is able to form images of objects — albeit 

 rather imperfect ones — it must not be supposed that Pilobolus can 

 see hke an animal. The simple eye or ocellus of Pilobolus is specially 

 adapted not for the perception of images but for the mechanical 

 perception of the direction of the strongest incident rays of light 

 by means of photochemical reactions. 



Fig. 52.^ — Pilobolus 

 longipes. Image 

 of letter A. Vide 

 text. Magnifi- 

 cation, about 30. 



