242 RESEARCH IN PROTOZOOLOGY 



will be made in Science. Fire-Toads can be imported from Europe 

 successfully, by parcel post or express, in tin containers only 

 slightly ventilated. Pack about a dozen or twenty animals in wet 

 sphagnum in each quart tin. If the toads are imported late in March 

 or early in April they will arrive before their breeding season in 

 May. To obtain eggs keep the toads in aquaria holding not less 

 than a cubic foot of water, with water weeds. Collect opalinid 

 cysts for infection of the tadpoles both from the sediment in the 

 aquaria and directly from the recta of the toads, of course after 

 the eggs have been laid. The toads while in captivity may be fed, 

 on the ground, with meal worms, flour-moth larvse, bot-fly larvae, 

 squirming pieces of earthworm (avoid Allolohophora foetida be- 

 cause of reported danger of heavy coccidiosis ; for the same reason 

 avoid the portions of the earthworms which contain the sperm 

 ripening pouches), or bits of meat. 



Metcalf (1923) describes the known species of opalinid^, 

 naming their hosts and the geographical occurrence of the hosts 

 and the parasites, so far as known. 



Opalinid material is easy to manipulate in cytological studies, 

 responding favorably to all the usual methods of treatment. Good 

 material of these parasites can be collected from well-preserved 

 museum or other specimens of anura, alcohol specimens being 

 much better than those in formalin. The hosts may be opened on 

 the ventral surface without real injury and the parasites removed, 

 with a very narrow section-lifter, from the rudimentary caecal 

 pouch at the upper end of the rectum (see Metcalf, 1923). 



The opalinid parasites of many anura are as yet wholly un- 

 known. Metcalf (1923) mentions all species which had been 

 searched for opalinids up to that time, and but few have been 

 explored since. Anuran tadpoles show shapes and conditions of 

 their opalinids very different from those seen in the parasites of 

 the adults. The life histories of the opalinids in the tadpoles are 

 peculiarly interesting {Cf., Metcalf, 1926) and should be studied 

 for each genus and most, at least, of the subgenera. Genetic rela- 

 tionships between hosts are commonly indicated by their parasites. 

 Studies of parasites are therefore interesting from the point of 

 view of the hosts, as well as for themselves. Much work from this 

 viewpoint should be done. The bufonid^, leptodactylid^ and 

 HYLiD^ are closely related families. Of these the genera of 

 BUFONiD^, other than Bufo, seem the most archaic. Their opalinids 



