228 C. CLIFFORD DOBELL. 
And hence, for my own part, I regard the conjugation of 
Trichomonas and Trichomastix as still undemonstrated. 
Negative evidence is, of course, always inconclusive. The 
fact that I have never found any conjugation in trichomonads 
after observing many, many thousands, proves nothing—save 
that the process, if it occurs, is very uncommon and difficult to 
find. But the difficulties I have met in the course of my 
researches have also shown me time after time the caution 
which is necessary in investigations of this sort. It is not 
justifiable from finding flagellates and cysts, or things like 
cysts, together in the gut contents, to connect the two with- 
out further evidence. As I have found only too often, it is 
necessary to study all the organisms which occur in the gut; 
and not only the organisms but also all cell-remains and other 
débris. Only by conscientious adherence to this slow and 
tedious method can satisfactory results be obtained. It is a 
pity that this elementary and obvious precaution has been so 
frequently neglected. 
(2) The Octoflagellate (Octomitus dujardini nom. 
nov.). 
Although this minute organism is the commonest of all the 
flagellates which are found in the large intestine! of frogs and 
toads, nevertheless it is the one which has given me the 
greatest trouble; and about its life-history I have been able 
to discover but little. On account of its very small size and 
very complicated structure it is not surprising to find that it 
has never been accurately described. None the less it has 
been named a great many times, with the result that the 
literature and the available facts relating to it are at present 
in a hopelessly chaotic condition. 
I will therefore first endeavour to summarise briefly the 
1 Since writing this account of the parasite it has been pointed out 
to me by Prof. Minchin that Danilewsky (‘ Parasitologie Comparée du 
Sang IT,’ 1899) observed the organism in the blood and body-cavity 
of sickly frogs, etc. This must be regarded most certainly, I think, as 
a pathological condition. 
