ORGANISATION 315 



till the fully-developed flagellate stage is reached. Multiplication may- 

 take place at any period of this development. All the intermediate forms 

 between the cyst and the elongate flagellates have been termed by Patton 

 (1909) pre-flagellates. Conversely, in the hind-gut the flagellate forms, by 

 a reverse process, become leishmania forms again. These eventually 

 encyst and escape with the dejecta of the insect. The forms between the 

 adult flagellates and the cyst have been styled 2^ost-flagellates. It is 

 doubtful, however, if the cycle, as, for instance, that of Crithidia gerridis 

 (Fig. 166), is as definite or simple as this nomenclature implies. If 

 nutrition is lacking in the intestine, it may happen that flagellate forms 

 become shorter and attach themselves to the gut wall. They have then 

 become post-flagellates, but a fresh supply of nutriment may lead them 

 to develop again into fully-formed flagellates. The terminology, however, 

 is not inconvenient, since the fully-formed flagellates in an insect, whether 

 of the leptomonas, crithidia, or trypanosome form, represent the height 

 of an infection. The rounded or short forms occurring before this stage 

 is reached are found in the stomach and are pre-flagellates, while those 

 developed after it in the hind-gut are post-flagellates. 



At certain stages of their development in the invertebrate the flagel- 

 lates may show a tendency to become attached to the lining cells of the 

 organs (gut, Malpighian tubes, salivary glands) in which they live (Fig. 

 150, 9-11, 21-23, 40-45)- This attachment, which takes place by the 

 flagellar end of the body, is associated with a change in morphology. 

 There is a loss of the flagellum, though the portion of the axoneme between 

 the kinetoplast and the anterior extremity of the body persists. In this 

 condition the flagellates may still retain the trypanosome, crithidia, or 

 leptomonas structure as far as arrangement of the kinetoplast, nucleus, and 

 undulating membrane is concerned. The attached flagellates are usually 

 subject to a shortening of the body, so that every transition between the 

 elongate forms and ovoid leishmania forms may be seen attached to the 

 surface of the cells. On the other hand, the posterior portion of the body 

 of the attached flagellate may undergo an overgrowth (Fig. 150, 12, 45). 

 An extreme type of this condition is seen in the case of the Cercoplasma 

 forms described by Roubaud (1908a, 19086, 1911a) for Herpetomofias 

 mirabUis and H. mesnili (Fig. 172), Similar forms were seen by Swingle 

 (1911) in the case of H. lineata, in which the post-nuclear part of the 

 body may reach a length of 300 microns. It seems to the writer that 

 the Rhynchoidomonas forms of Patton (1910a), in which the axoneme 

 terminates at the anterior end of the body, are probably attachment forms 

 of a flagellate of the trypanosome type (Fig. 150, 45, Fig. 174). In these 

 there is a certain degree of overgrowth of the posterior portion of the body, 

 though nothing comparable with that which occurs in the Cercoplasma 



