N. H. SWELLENGREBEL 
109 
the study of these two forms may help perhaps to gain a better 
knowledge of some details of the structure of these flagellates. 
There is still some doubt in conuection with the following points ; 
1. The division of the flagellum. 
2. The number of flagella in non-dividing individuals of the genus 
Herpetomonas. 
3. The sexual phenomena occurring in the genera Herpetomonas 
and Grithidia. 
4. The occurrence of a true trypanosomiform-stage in the life-cycle 
of Grithidia. 
Although I am quite aware of the fact that my observations do not 
clear these questions, they may, perhaps, help other workers to do so. 
Before proceeding to the description of these flagellates, I will say 
a few words on the technicpie employed. I fixed the preparations of 
the contents of the gut either by the wet or by the dry method 
(employing corrosive alcohol and absolute alcohol respectively), and 
stained with iron-haematoxylin, or Giemsa’s solution. Iron-haematoxylin 
is liable to give misleading results as some parts of the cell {e.g. the 
achromatic portion of the blepharoplast) become decolourised during 
the act of differentiation. Preparations stained by this method are not 
so trustworthy as those stained with Giemsa’s solution (after wet or 
dry fixation). 
In a previous paper (1910) I have carefully compared the relative 
value of the different methods of wet and dry fixation, consequently I 
need not dwell on this subject. I wish, however, to challenge a criticism 
of Jollos’ (1910) concerning my paper on the technique of fixation and 
staining. This author states that only the sti'ucture of the nucleus is 
of any value if one wishes to compare the different methods of fixation. 
I think this view is wrong; of course the nuclear structure is very 
important, but in judging of the relative value of a fixative one should 
take into account its influence on the whole cell and not only on the 
nucleus. Jollos states that Giemsa himself has clearly shown the 
uselessness of the old method, but in reality he has only shown that one 
should not make dry preparations of A moebae, whereas my paper refers 
to trypanosomes. Lastly, Jollos thinks the drawings I published to 
corroborate my views on the equivalent value of wet and dry fixation 
are not trustworthy because they are not to be compared with Minchin’s 
figures. This is quite true, as my drawings were simple zincographic 
reproductions, whereas Minchin’s paper (1909) is accompanied by 
lithographic plates; but apart from this difference, which is of no 
