RESEARCH PROBLEMS IN THE OPALINID^ 243 



are wholly unknown. Anyone having specimens of any of these 

 archaic bufonids should study their opalinids. This is the most 

 important group of unexplored genera. But any unexplored anuran 

 is likely to yield opalinids of interest, perhaps of very marked 

 interest. Metcalf (1923) shows how geographic distribution of 

 the hosts compared with the host-occurrence and geographic dis- 

 tribution of the parasites may be made very significant, and Metcalf 

 (1929) reviews similar use of host-parasite data for all groups. 

 Preserved specimens of anura, especially if preserved in alcohol, 

 generally have their opalinids in good condition for study. Often 

 the chromosomes can be counted in such specimens. Opening the 

 specimens does not really injure them for museum purposes. There 

 is thus here a great source of material waiting in many museums 

 for study. 



