Opalina. 205 
To obtain sections of the gametes, whole recta of infected tad- 
poles were cut. The dirt in the rectum usually prevents cutting 
sections thinner than 3, 4, or 5 micra, but these suffice. 
Sections were stained with DrvarieLy’s haematoxylin, Herpern- 
HAIN’s iron-haematoxylin, GRENACHER’s borax carmine, safranin, 
safranin and light green (Lichtgriin), thionin, gentian violet, methyl 
violet, methylen blue, methyl green, eosin, dahlia, orange G, fuchsin, 
magenta, Kernschwarz, Bionpt-Exriicn-HEmENHAIN’s mixture. Enr- 
Licn’s triacid mixture and Earuicn’s indulin-aurantia-eosin mixture. 
All gave results of some value and the comparison of the results 
obtained from different stains was important, especially in studying 
the refractive spherules. Dernarreyy’s haematoxylin and HetrpEn- 
HAIN’S iron-haematoxylin were the most generally useful stains. The 
most differential stain was obtained with safranin and light green 
(safranin 12 to 24 hours, light green in 95°), alcohol '/, to 3/, of a 
minute). The results with all of the stains used are shown in a 
table in the appendix. 
For illumination the light from a Welsbach gas mantel was 
used, daylight not being strong enough. 
The degree of accuracy of the figures is told in each instance 
in the explanation of plates, any figures, or parts of figures, schemati- 
cally drawn being so indicated. 
Since writing the major part of this paper I have found that 
smear preparations of undiluted rectal contents of Rana temporaria 
give fine results with cysts and free swimming individuals of 
O. ranarum and I do not doubt that equally good results would be 
obtained with other species. The method should be of especial 
value with the minute forms in the recta of tadpoles. The smear 
preparations should not be allowed to dry, but should at once, while 
moist, be fixed a moment in a hot fixing fluid and then be trans- 
be used for storing small objects in alcohol has also proven very useful. Much 
of my Opalina material has been kept in gelatine capsules in a jar of 95°/, Alcohol. 
(Alcohol weaker than 80°, softens the capsules.) A further suggestion, from Dr. 
R. Dowrn and Dr. Gast, that the lower half of the capsule be sealed with celloidin 
before covering with the lid is important, since with very small objects there is 
danger that some may get between the capsule and its lid and be crushed. Be- 
fore adding the film of celloidin, it is well, as Doctors Donrn and Gasr suggested, 
to puncture the capsule in several places just below its upper edge with a needle, 
so that the celloidin film will hold firmly. Minute objects so stored transport 
without danger of breakage and the capsules require much less room than the 
glass tubes ordinarily used. Furthermore there is no cotton plug in which any 
of the objects may be lost. 
