1917] McCulloch: Crithidm euryophthalmi 87 



Eectal Forms 

 In a few cases the preparations made from the rectum and con- 

 tents have shown a few oval spore forms (figs. 28, 35). The origin 

 of these is not clear but it is possible that they are zooids which have 

 been somewhat protected by a thicker membrane and consequently 

 are more resistant. As previously mentioned they retain the haema- 

 toxylin stain relatively longer than any of the other forms or zooids 

 in particular. Whether these spore forms become protected by a 

 thick membrane through which the stain does not readily penetrate is 

 an open question. Some spore forms found in rectal preparations 

 do not take the stain. 



Infective and Degenerative Cycles 

 The question regarding the part played by the small zooids which 

 arise from the process of internal budding in the life cycle is of great 

 interest. Do they develop into flagellates or do they remain zooids, 

 migrating back to the posterior parts of the intestinal tract to form 

 the rectal spores ? Preparations show that the zooids are exceedingly 

 numerous in the mid-stomach and pyloric expansion. Because of 

 their numbers and the same characteristic structure found through- 

 out, the zooids are regarded as infective forms. They become deeper- 

 staining upon reaching the rectum. All the forms which do not 

 remain as non-flagellated forms constitute what we have designated 

 the degenerative cycle. The flagellates of the mid-stomach and of 

 the pyloric expansion shoM^ signs of degeneration. They become 

 vacuolate. The nucleus may show a diffuse structure. Bacteria may 

 adhere to the sticky periplast or the cytoplasmic part may disappear 

 entirely leaving only the skeleton of the nuclear structures. No 

 stages of encystment of haptomonads have been observed. All the 

 nectomonads and haptomonads become degenerate. Flagellated 

 forms in C. euryophthalmi do not become spores in so far as our 

 investigation has gone. 



Summary 



1. The differences existing in the morphology and life cycles of 

 the two flagellates found in Leptocoris trivittatus and Euryophthal- 

 miis convivus have been deemed sufficient to justify our classifying 

 them as two distinct species, namely, C. leptocoridis and C. eury- 

 ophthalmi. 



2. The digestive tract of Euryophthalmus convivus consists of 

 fore-gut divided into oesophagus and proventriculus ; the mid-gut. 



