Opalina. 199 
preserved material. These parasitic animals do not live long outside 
the host. In water they live usually about one day; in water 
containing some of the rectal contents and part of the rectum of the 
host they may live two or three times as long. In 0.6°/, Sodium 
chloride solution they live generally about two days. If part of the 
rectum of the host and a little of the rectal contents be added to 
the salt solution the animals live longer, from three to nine days. 
Locke's fluid!) semes about as favorable a medium as physiological 
salt solution.?) Opalina obtrigona lived longest in my cultures. 
Opalina caudata seemed generally the most delicate, though I have 
several times kept it seven days. Occasionally I have had all the 
animals in a culture die in less than a day, some change in the 
rectal contents doubtless occurring which poisoned the Opalinae. 
Often some individuals in a culture will live after many others 
have died. Generally, for a day or two before the Opalinae in a 
culture die, they will show gradually slower and slower movements. 
Abnormal nuclear conditions are found in these dying animals, as 
will be described in the chapter on abnormalities. 
It is interesting to note that keeping the animals outside the 
host tends to cause division, perhaps through the unfavorable environ- 
mental conditions. 
Large watch-glasses were used to contain the cultures of adult 
Opalinae, these glasses bring covered to prevent evaporation. Attempts 
to rear isolated adults in microscopic aquaria (hollow-ground slides) 
were not made; such attempts with the gametes and zygotes were 
unsuccessful. These are more delicate than the large forms, so 
that very likely the latter could be kept alive a couple of days or 
so in such microscopic aquaria. 
For the study of living gametes and other minute forms from 
the tadpoles, slide cultures were used. The intestine of the tadpole 
would be placed upon a slide with a drop or two of 0.6%, NaCl 
1) Calcium chloride (anhydrous) . . . ... 007% 
POLASSIUM ‘CHIGHGG. 5. 5. ete ce ow, ee ONG 
Sodiunr' chigridery 67729) 5 feet BE OG or 
Sodium bicarbonate. . . . . . 0,01—0.03 %. 
From Journ. of the Boston Soc. of Med. es, 1896. 
*) Piévrer (1905) says that the best culture medium for Opalina is made of 
sodium chloride 0.8% . . . . aire, 77 LOULparis 
sodium and potassium tartrate 30%. ogee, iar 
distilled water. . . . 400 
and that in this fluid, when it contain no ee baygen Opalina, if fed, will live 
three weeks. I have not tried this fluid, nor used any oxygen-free paliire media. 
