FUNGOID GROWTHS ON APHIDES. 19 



fruit is identical in size and form with the fruit of 

 Peronospora infestans.''^ 



These observations, accompanied by a characteristic 

 woodcut, may be found in the ' Gardener's Chronicle ' 

 for April 8th, 1876. 



Without calling in question the ability of Mr. W. G. 

 Smith at once to recognise a mycelial thread, 1 may 

 state that a view of the above drawing of the leg of 

 an infested Aphis at once suggested to me the nervous 

 filament or filaments that may be traced in the legs 

 of almost every full-grown living Aphis, reaching from 

 the coxa to the tarsal claws. The same drawing also re- 

 called to my mind the nervous filaments which proceed 

 from the ganglionic mass situated in the head of the 

 insect, and which extends throughout the length of the 

 antennas to the tip. 



Once more, it should be borne in mind that the 

 bodies of Aphides are largely supplied with tracheal 

 tubes. Although these silvery threads seem to want 

 the spiral fibre by which tracheae can be identified in 

 most insects, the true functions of these threads in 

 Aphis can be certainly known from the fact that they 

 uniformly take their rise from the respiratory stomata, 

 as is shown in Plates B and C in the first volume of 

 this Monograph. 



The fact that oogonia and mycelium are present in 

 the microscopic slides containing the Aphides in 

 question need cause no surprise, if we consider that the 

 insects examined possibly were bred on potatoe leaves 

 infected by the Peronospora. 



On the other hand, the history of Muscardine and 

 Botrytis hassiana in the silkworm; of Empusa, the 

 fungus of the house-fly ; and the occurrence of fungoid 

 growths on living animal tissues of low vitality, will 

 make less strange or improbable to us the a|)pearance 

 of similar growths on Aphides. Furthermore, on the 

 leaves of peach trees in summer, often may be found 

 isolated specimens of Bhopalosqjhum dianthi, whose 

 bodies have been entirely destroyed by what would 



