422 Journal of Agricultural Research voi. xvni, no. s 



of aggregations or complexes possible. Furthermore, since the blood 

 corpuscles possess amoeboid movements and are carried from place to 

 place by the circulation of the blood, the formation of the cystlike aggre- 

 gations is easily understood when this attractive force, perhaps chemo- 

 taxis, is considered. 



Whatever the force may be, the fact remains that plasmodia are 

 formed, evidently for the purpose of destroying the fungus cells. It 

 has been shown, however, that the latter are more potent than the 

 leucocytes, which ultimately disintegrate; so that while the act of 

 phagocytosis is undoubtedly present and may impede the progress of 

 the disease in cutworms, it can not be considered a successful defensive 

 process in the present instance. 



The same statement may be made in regard to those nonsusceptible 

 insects into whose bodies a large number of conidia were injected and 

 which, it wUl be remembered, were unsuccessful in combating the 

 fungus. When a small number of conidia were injected into the blood 

 of such nonsusceptible hosts, however, it is evident that something was 

 present which was sufficiently potent to render the fungus cells innocuous. 



From the discovery of phagocytosis in cutworms parasitized by 

 Sorosporella, it is reasonable to assume that it ma}' be present in other 

 insects attacked by other fungi. It is furthermore not unlikely that the 

 relative potency of the phagocytes and fungi may vary according to the 

 insect and fungus. 



Those who have ever attempted to spread entomogenous fungi in the 

 field in an attempt to control insect pests have invariably found many 

 problems relating thereto apparently inexplicable. A further study of 

 phagocytosis may assist in solving these questions. It may explain, 

 for example, why certain individuals or species are immune and others 

 susceptible and why the period of incubation may vary to such a degree 

 in the same disease. From a broader point of view it is not impossible 

 to believe that it will likewise explain why insects appear more suscep- 

 tible under certain apparently favorable weather conditions than under 

 unfavorable conditions. 



CULTURE OF THE ORGANISM 



Immediately upon the receipt of the first infected cutworms from 

 College Park, Md., attempts were made to cultivate the organism on 

 artificial nutrients. The plate separation method was at first employed 

 to isolate the fungus; but later it was found, as has been previously 

 noted, that pure cultures could be readily obtained by transferring 

 groups of resting spores directly, with a sterile needle, to sterile plates 

 or tubes. 



When first transferred from its natural host to artificial media the 

 organism grows very slowly, and on potato agar it develops less luxu- 

 riantly than on any other medium employed. Unfortunately potato 



