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THE AMEBIC AN NATURALIST [Vol. LIV 



ferring to the separation of the epithelium from the basement 

 membrane, he states : 



In one ease the separation of the epithelium is taken as evidence of 

 invasion, and in the other it is taken as evidence of escape of the 

 flagellates from the tissue. 



Dr. Tyzzer quite mistakes the point involved. It is not the 

 separation of the epithelium that is the important point (since 

 this is often an artifact), but the orientation and grouping of 

 . the parasites in the vicinity of this epithelium. By looking at a 

 church door we can scarcely tell whether the last congregation 

 went in or out, but if we can find the congregation the question 

 will probably be answered. 



And in further criticism of this point (avenue of infection 

 and of exit) Dr. Tyzzer has the misfortune to state, 



The organisms interpreted by Hadley as encysted forms of the flagel- 

 late being discharged from the tissue are evidently Blastocysts derived 



Did Dr. Tyzzer fail to examine the writer's photomicrographs 

 (Bulletin 168, Figs. 30, 32 and 36) together with the complete ' 

 description of these figures on a preceding page? Did he fail 

 to read the description of this ' 1 reversed infection ' ' on page 26 ? 

 Are the writer's photographs so poor as to make possible a con- 

 fusion between a flagellate trophozoite and "Blastocystis," or 

 has Dr. Tyzzer an inadequate conception of what Blastocystis 

 really looks like? And, in addition, may it not be a little inac- 

 curate to affirm that "there is now quite general agreement that 

 they (Blastocystis) represent a distinct type of organism . . ."? 

 The matter is apparently still in controversy. 



As to the statement of Dr. Tyzzer that the writer has failed 

 to establish the identity of the parasite with any species of 

 Trichomonas, or "to demonstrate any features characteristic of 

 the genus," — this must be left for others to judge. But the 

 author can not forbear to reiterate that he has no reason to 

 withdraw the evidence presented in previous papers. The 

 strongest evidence of all comes from the relatively rare cases in 

 which one can trace from the beginning the movements of the 

 parasites in the tissues, and follow clearly the morphological 

 changes that they undergo as the infection proceeds.' It would 

 seem that Dr. Tyzzer, in his examination of only "five infected 

 turkeys, " has never seen such cases. The present writer worked 

 for many years before he found the ideal specimens. It is a 



