204 : C. CLIFFORD DOBELL. 
5. Bursaria(?) cordiformis Ehren- 
berg. ‘ é = Nyctotherus cordiformis. 
6. Bursaria nucleus Ehrenberg 2 
7. Bursaria entozoon Ehrenberg J 
8. Vibrio bacillus O. F. M. tr 
= Balantidium entozoon. 
Though necessarily imperfect, and in many cases highly 
fantastic, the descriptions of Hhrenberg remain in many ways 
a model of accurate and careful observation. 
From the time of Ehrenberg down to the present day this 
little group of protists has received—with one exception— 
but scant attention. The exception is Opalina, of whose 
life-story, owing to the admirable researches of Zeller, 
Neresheimer (40),' Metcalf, and others, we now have a fairly 
perfect knowledge. As for the remainder, so little of the 
life-history has been discovered hitherto—the observations 
on them being mainly published in the form of short notes— 
that I will not discuss them further here. 
MareriAL AND Metruops. 
The methods employed in the following researches have 
been, for the most part, the same as those which I have 
already described in a previous paper (10), to which the 
reader is referred. JI will here add only a few remarks 
regarding one or two special points. 
The frogs and toads have all been obtained either in 
Cambridge or in Munich. JI have worked upon Rana tem- 
poraria L., R. esculenta L., and Bufo vulgaris L. As 
I have carried out the researches in two different laboratories 
the optical apparatus employed has been somewhat varied. 
But that has made no difference of any importance. ‘The 
objectives, etc., employed will be found in the explanation of 
the figures, likewise the technique for fixing and staining. 
I may add, however, that the best fixation has always been 
obtained with Schaudinn’s sublimate-alcohol, and the best 
staining with Heidenhain’s iron-alum hematoxylin or Dela- 
1 A complete list of the literature on Opalina will be found appended 
to the work of this investigator. 
