ioo SOME MINUTE ANIMAL PARASITES 



is set free, in part, during certain stages of fever, 

 and then some of it is taken up by the leucocytes of 

 the blood, which consequently become pigmented. 

 Doctors make use of the discovery of pigmented 

 leucocytes in many cases in which it is difficult to 

 discover parasites in the blood of the patient. 



Sometimes the examination of suspected mosqui- 

 toes for stages in the life-history of the parasite 

 does not show the characteristic cysts full of 

 sporozoites in the stomach wall of the Anopheline, 

 but instead there are dark blackish bodies about the 

 same size, but harder and coarser. These are the 

 structures that the discoverer of mosquito-borne 

 malaria, Sir Ronald Ross, termed " black spores. 

 Even now there is some uncertainty as to what the 

 nature of these black spores really is, but in all 

 probability they represent cysts that have failed to 

 break through into the body cavity, and so have 

 perished in the walls of the stomach. Some workers 

 believe them to be Protozoa belonging to the genus 

 Nosema, and then they are regarded as parasites of 

 the malarial parasites. 



It is very important, in dealing with insect-borne 

 diseases, to determine whether the winged carrier is 

 able to transmit the disease to its progeny, and also 

 whether the invertebrate, once infected, remains 

 infective for life. Little is known of this aspect of 

 the malaria-transmitting Anophelines, but so far no 

 evidence of hereditary infection has been found, and 

 experiments are lacking as to the period during 

 which the fly remains infective. The adult male 

 fly lives only a very short time after mating. The 



