232 The Philippine Journal of Science 1918 



might be, as I have already said, a reduction process preliminary 

 to the formation of flagellated gametes. 5 



Following the copulation of these flagellated cells, Hadley men- 

 tions the formation of a viscid membrane around the organisms, 

 which have meanwhile rounded off. This might coincide with the 

 process described by Schaudinn(45) mentioned previously. Fol- 

 lowing conjugation, adds Hadley, the membrane hardens to form 

 a firm cyst. The single cysts, he says, measure from 10 to 12 

 /i, but in the "fused" or conjugated forms the cysts may reach 

 a size of 20 to 30 /x. "Double" or "triple" cysts, he concludes, 

 may represent a division of the original cysts, whereupon each 

 cyst continues to produce daughter cells independently. 



This stage of the life cycle, according to Hadley, is the one 

 usually encountered and which has caused Trichomonas to be 

 regarded as a harmless commensal ; but he goes on to show that 

 in another phase of activity the parasite may penetrate the 

 epithelium and cause fatal lesions in the intestinal tract. The 

 question is, what stimulus is it that causes the organism so 

 radically to alter its mode of life. To my mind this very ques- 

 tion is to-day one of the most important problems of parasitology. 



In the turkeys observed by Hadley the invasion was invariably 

 preceded by diarrhoea with an accompanying increase in the 

 number of parasites as the disease advanced. The parasites 

 appear not only in the liquid csecal contents, but in the depths 

 of the caecal tubules or crypts and finally in the tissues behind 

 the epithelial walls. Hadley states that by a process of "auto- 

 gamous reproduction" the mucosa, submucosa, and muscularis 

 mucosae and even the muscular layers are successively invaded, 

 until the whole caecal wall is involved. Secondary bacterial in- 

 vasions may supervene to bring about results that are almost 

 invariably fatal. Here Hadley raises the old question as to 

 whether the vast numbers of parasites present are the cause or 

 the result of the diarrhoea. This point will be further discussed. 



5 In a recent letter to me, Doctor Hadley says: "Regarding the presence 

 of syngamy in the reproductive process, I doubt very much that it occurs 

 in the flagellated swarmers. I have never seen the least suggestion of it. 

 I am rather of the opinion that, when it occurs at all, it takes place in 

 the stage after the organism has lost its chief features of flagellate mor- 

 phology, has become globoid and possesses a more or less viscid capsule 

 or membrane. In fresh preparations such appearances, at least in the 

 first adhesive stages, are fairly common." It is a matter of great regret 

 to me that three other papers by Doctor Hadley, dealing with this subject, 

 reached me too late for consideration in connection with this paper. They 

 should be consulted by all who are interested in the subject. [See Bull. 

 Agr. Exp. Station, Rhode Island State College, Kingston, R. I. (1916), 

 Nos. 166 and 168, and Journ. Med. Res. (1917), 36, 79.] 



