1915] McCulloch: Crithidialeptocoridis 11 



may take place within the plasmodial mass. If a plasmodial mass re- 

 mains intact until the flagellates reach maturity, this might be one 

 explanation of the aggregation rosettes found in Grithidia leptocoridis. 

 On the other hand, such an aggregation rosette can be looked upon as 

 an epithelial cell which, upon being separated from the rest, rounded 

 up and the great mass of flagellates still remain attached as when it 

 was a part of the lining of the digestive tract. 



In these multiple fission forms or merozoites the nucleus is always 

 present in the extreme posterior end and the "kinetonucleus" lies a 

 little anterior within the characteristic light area. The flagellum is 

 present, being coiled back upon the body to which it adheres for some 

 time. Later the cytoplasm parts and the flagelliun straightens out. 

 At first, there are slow contractions of the body, but the flagellum soon 

 becomes more active and the organism darts off across the field after 

 many ineffectual efforts. The rhizoplast can be demonstrated without 

 difficulty in these forms, but there is no additional structure which 

 might be looked upon as an "axostyle. " Among these merozoites 

 longitudinal division probably occurs as seen in plate 2, figures 28 

 and 46. 



3. The Flagellate Stage (Vegetative Phase) 

 The flagellates arising from the multiple fission forms and likewise 

 from preflagellate forms which do not undergo the multiple fission 

 process, migrate posteriorly into the mid-intestine, ilium, colon, and 

 rectum. These are the flagellates of the vegetative phase, and since 

 their structure has already been described only some of the important 

 variations in size will be taken up here. 



The flagellates vary in length from 20 to 40 y. and from 1.5 to 

 3 in width (pi. 2, figs. 54, 56; pi. 3, figs. 57-62). The extremely long 

 forms (pi. 3, figs. 60-62) are always found in the ilium and colon. 

 In a few instances these have been found attached to the wall of the 

 colon for a time. 



4. PostflagelLjVte Stage (Rectal Phase) 

 The postflagellate forms are found in the rectal region. Soon after 

 the migration of the flagellates posteriorly to the mid-inte.stine, ilium 

 and colon, there are a few which make their way at once into the 

 rectum. As the insects become mature the rectum is apt to be lined 

 with attached flagellates and the lumen filled with a different type of 

 the parasites, the free forms. 



