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Loa papionis n. sp. 
II. Description of the ova and larvae of Loa papionis 1 . 
Technique. I shall confine myself to pointing out a few slight modifications 
in technique which seemed to me to increase the efficiency of certain of the 
methods available in 1914. For further details, see Langeron (1916). 
I. The staining of dry blood-films. When using Pappenheim’s panoptic 
method I obtained the best results by staining for twenty minutes with a 
solution of Giemsa of half the ordinary strength. 
II. Wet fixation. Looss (1914), in describing his method, says that the 
film is apt to become detached if slides are used and recommends coverslips; 
I have not found this to be the case and prefer slides, which are easier to 
manipulate. 
III. Treatment after wet fixation. Although Heidenhain’s iron haematoxylin 
method is usually employed after wet fixation, Giemsa, Azur II, and Carbol- 
methylgreenpyronin also give excellent results. Preliminary overstaining, 
followed by differentiation with 90 per cent, alcohol, enable every detail to 
be seen at one stage or other of the process; moreover preparations which keep, 
at any rate for some months, may be made by mounting in paraffin oil and 
cementing the edges of the coverslip. 
IY. Mensuration. The measuring of living embryos or larvae is rather 
tedious, and it was found impossible to determine their dimensions with 
absolute accuracy owing to the waves of contraction which are constantly 
passing along their bodies. However the measuring of the dead material 
1 The difficulties in the way of an accurate naming of the forms circulating in the blood, are 
considerable. For example, in the nematode family we are considering, it is sometimes impossible 
to say whether the sheath present in blood-films represents the true egg-membrane or a moult; 
i.e. we are unable to say whether the organisms in question are eggs or not. Moreover the term 
“embryo ” is often used rather loosely, descriptions of sheathed and sheathless embryos being 
commonly met with, both in the literature and in text-books. Again, Stephens (1916) asserts 
that in many parasitic nematodes the young must be called “ larvae ” even before they have left 
the egg-shell, for they present characters which are subsequently lost. Under these circumstances 
conventions are essential if confusion is to be avoided. In this paper, I shall use the terms “ ovum ” 
and “embryo” so long as the existence of the egg-membrane is certain. When the membrane is 
absent, or when it is doubtful whether the membrane present represents a moult or not, I shall 
use the term “larva.” In other words: 
(a) The use of the terms “ovum” and “embryo” is restricted to the forms present in the 
female genital tract. 
(b) Sheathless forms from the genital tract, together with all forms present in the blood 
of the definitive host, are referred to as “larvae.” 
Yet another difficulty occurs when the adult form is unknown. This was originally met by 
the coining of the term “microfilaria” qualified by some non-committal name— Microfilaria diurna 
for example. At a later period, however, Mf. diurna was identified as being the offspring of Filaria 
loa, while a new genus was constituted consisting of a single species— Loa loa. In consequence of 
these discoveries and changes in nomenclature, Microfilaria diurna is now correctly referred to as 
Microloa loa. 
