200 SCHAUDINN'S RESEARCHES [CH. 



IV. APPENDIX. The Blood Parasites of Athene noctua. 



In addition to the above-mentioned infections, it is 

 probable that most of the blood parasites of birds are trans- 

 mitted by the agency of some species of mosquito. Schaudinn, 

 in his famous memoir on the life-cycles of the parasites of the 

 Little Owl (Athene noctua], described the development of 

 these organisms in the alimentary canal of the common gnat, 

 Culex pipiens. 



The Little Owl harbours in its blood at least six forms of 

 avian parasites, namely, (i) a proteosoma ; (2) a halteridium ; 

 (3) a small form of trypanosome ; (4) a large form of trypano- 

 some ; (5) a leucocytozoon ; and (6) a spirochaete. 



According to Schaudinn all these forms belong to the life- 

 cycle of only three species of parasites. The proteosoma is 

 certainly a distinct form unrelated to any of the others. On 

 the other hand the halteridium and the small trypanosome 

 were said to be phases of the same parasite, whilst the large 

 trypanosome, leucocytozoon and spirochaete were considered as 

 stages in the development of another parasite. 



The halteridium was supposed to be the resting intra- 

 corpuscular stage of the small trypanosome, which at night 

 developed a locomotor apparatus, became free from the red 

 cell and swam about as an ordinary trypanosome ; in the 

 morning it penetrated another red cell, its locomotor apparatus 

 disappeared, and it again became a halteridium. Three forms 

 of the parasite were distinguished, known respectively as male, 

 female and indifferent forms. The latter were the forms which 

 multiplied in the blood, and from these small trypanosomes 

 either indifferent, male, or female forms, might develop. 



The two latter developed slower than the indifferent forms, 

 and as they grew larger were unable to change from the hal- 

 teridium to the trypanosome form, but became exclusively 

 intracorpuscular or halteridium forms. The further develop- 

 ment of these sexual forms could only take place if they were 

 ingested by a gnat, Culex pipiens. In the alimentary canal 

 of this insect the male and female forms became free and 

 copulated, forming typical ookinetes. The latter developed 



