64 E. H. STRICKLAND 
’06 for Pleistophora periplanetae proved somewhat superior be- 
fore staining with an eosin-azure mixture. With this method a 
smear is made on a cover glass and allowed to dry. It is then 
immersed in absolute alcohol for ten minutes and again dried. 
Perrin then stained over night in one of Giemsa’s preparations, 
after which the slide was washed, dipped for a moment in absolute 
aleohol, rewashed and mounted in cedar oil. 
Stains. For general histological purposes Heidenhain’s iron 
haematoxylin in combination with orange-G proved to be the 
most satisfactory. This combination, however, is almost useless 
for studying the nuclear matter of the spores, for the cytoplasm 
takes up the haematoxylin as readily as does the nuclear matter 
and it cannot be again washed out. The usual stain for this 
purpose is Giemsa’s ‘Eosinazur’ stain. The blue of this mixture 
however proved to be too intense. Other Giemsa preparations 
were not altogether satisfactory and I finally found it preferable 
to stain separately with azure 1 and eosin A.G. and to differ- 
entiate by overstaining with a 0.8 per cent aqueous solution of 
azure 1, rapidly washing with water and then dehydrating. The 
absolute alcohol contains a saturated solution of eosin and the 
slide can be left in it for about five minutes after which it is 
immersed in xylol and examined in it as a medium. The nuclei 
of the spores have a strong affinity for eosin which can be readily 
washed out of the other tissues with water. If the blue be too 
intense it can be washed out in alcohol. By overstaining with 
both azure and eosin and bearing in mind that the former can be 
washed out most readily with alcohol and the latter with water, 
one can, with a little practice, get both stains nearly counter- 
balanced. 
THE MICROSPORIDIAN AND OTHER PARASITES OF SIMULIUM 
LARVAE 
The earliest account of a Microsporidian parasite of Simulium 
larvae that I have been able to trace was that of Léger ’97. He 
describes a Glugeid, G.varians, parasitising the larvae of 8. 
ornatum, a species common in France. In 1904 Lutz and 
Splendore described various forms of Glugeids found in the larvae 
