0. Dobell 
177 
description is far from clear, and in some ways even contradictory. Neverthe¬ 
less, they may, I think, not unfairly be given the benefit of the doubt; and 
I shall therefore assume that their organisms were the same as those discovered 
by Kjellberg, seen later by Bimer, and rediscovered and first accurately 
described by Wenyon. It will be noted that even if we reject Rivolta's name, 
and accept that of Railliet and Lucet, the name of the organism itself will still 
be the same —Isospora hominis —differing only in the name of the authority 
cited for it. The fact that this name should have been twice introduced for 
parasites possibly identical with Wenyon’s, and not certainly identifiable with 
any other organisms, supplies a sufficient reason, I think, for its retention in 
B 
Fig. 1. Fully developed oocysts and spores of Isospora bigemina (A) from cat, and I. homims 
(B) from man. Camera lucida drawings. Magnification approximately 2000 diameters. 
this sense; whilst to abolish it could serve no useful purpose, and might even 
lead to greater confusion in the future. 
We have already seen that many authors have asserted or conjectured that 
the Isospora, which they believed to occur in man, is the same as that occurring 
in cats and dogs 1 —namely, Isospora bigemina. Bor such a view there is not a 
vestige of evidence. In appearance the oocysts found in human faeces are 
quite unlike those from the faeces of the cat (cf. Text-fig. 1, A and B). The 
latter are usually much larger, though subject to great variation in size; their 
walls are thicker, and brownish in colour; and they are plumper and more egg- 
1 It may be pointed out that there is still no really conclusive evidence to prove that the 
Isospora of the cat is the same as that of the dog, or that both are merely varieties of one species. 
It is quite possible that they are distinct species. The matter requires further investigation. 
12—2 
