174 University of California Publications in Zoology [VOL. 19 



HAPTOMONADS 



One of the most characteristic features of the life cycle of a crithi- 

 dial flagellate is the great mass of attached forms which line definite 

 parts of the digestive tract of the host. Minchin and Thomson found 

 three regions of the digestive tract of the rat-flea where the crithidias 

 of Trypanosoma lewisi might attach themselves, namely, the prepyloric, 

 post-pyloric, and the rectal regions. In the lupine bug there are like- 

 wise three regions where the haptomonads may attach themselves : ( 1 ) 

 in the posterior part of the "crop," where they are possibly com- 

 parable to the prepyloric crithidias in the posterior part of the 

 stomach of the flea; (2) in the posterior half of the mid-stomach, 

 where they are probably comparable to the post-pyloric crithidias 

 of the rat-flea, attached to the anterior part of the intestine; and (3) 

 in the pyloric expansion, where they are comparable to the hapto- 

 monads of the rectum of the rat-flea. In Trypanosoma lewisi in the 

 flea these investigators regard the prepyloric haptomonads as being 

 due to a forward migration from the rectum,. possibly as a result of 

 the food conditions. The prepyloric haptomonads are not found fre- 

 quently in the flea, and in only one preparation of the "crop" of the 

 lupine bug were haptomonads found. In the lupine bug haptomonads 

 were found in a number of preparations of the mid-stomach, but they 

 were commonly present in preparations of the pyloric expansion. The 

 haptomonads observed in the single preparation of the "crop" were 

 of the rectal type, small oval forms similar to those from the pyloric 

 expansion shown in plate 6, figures 107 and 117. The serial sections of 

 the digestive tract, however, showed no haptomonads in the "crop." 



From the serial sections of the mid-stomach abundant material 

 was obtained for the study of the haptomonad of this region. The 

 attached forms here (pi. 6, figs. 93-96) are relatively small, slender 

 flagellates. They are uniform in size and shape, on the whole, and 

 form a definite fringe on the inner surface of the epithelial lining of 

 the sections of the mid-stomach. These flagellates attach themselves 

 to the epithelial cells by means of the flagella. They frequently almost 

 surround the elongate, columnar epithelial cells, which project into 

 the lumen of the digestive tract. The grooves between masses of epi- 

 thelial cells evidently afford a particularly good place for the hapto- 

 monads, since they are found in compact layers in such places. Hapto- 

 monad crithidias of this type are the only ones found in the mid- 

 stomach and they continue to line the digestive tract posteriorly 



