THE OPALINID CILIATE INFUSORIANS. 389 



110 Zellcriella (omitting doubtful identifications) which is known 

 from more than one genus of host, and only two species of Protoopa- 

 lirui. In both these cases of Protoopalina it seems possible that the 

 reports are based upon insufficient scrutiny in identification or upon 

 temporary infections. If, after further observation, the several 

 binucleated species of Opalinid prove not to be normally parasitic 

 in hosts belonging to more than one family, we have a strange con- 

 dition of a wider range of infection by single species among the 

 multinucleated Opalinids than among the more archaic Protoopalinas 

 The point is of sufficient interest to caU for further observation. 



8. THE OPALINID PARASITES AND THE GEOGRAPHICAL LOCALITIES 

 OF THE SEVERAL SPECIES OF HOSTS KNOWN TO BE INFECTED 

 BY OPALINIDS. 



In the last chapter we have looked at the host-parasite relation 

 chiefly from the point of view of the parasites. We should also give 

 the data from the standpoint of the hosts. There follows a tabular 

 statement giving the name of each host whose parasites were studied, 

 the place and date of its collection, the name of the collector, usually 

 the museum catalogue number of the preserved specimen, and the 

 species of Opalinid parasite found. Some additional items may also 

 be given. Most of the hosts studied were museum specimens which 

 had lain, often for many years,*^ upon the shelves of the United 

 States National Museum. If the specimens had been preserved 

 originally in alcohol and had been kept in this fluid, their para- 

 sites were generally well preserved, even in some cases in which 

 the alcohol had become weak and the tissues of the host had softened. 

 Specimens preserved in formalin, on the other hand, rarely yielded 

 Opalinids or other intestinal parasites, even though the specimens 

 had later been placed in alcohol. No data as to methods of preserva- 

 tion are given usually upon the Museum records, so this feature is 

 seldom mentioned in the table. It is readily seen that negative 

 records mean little under these conditions, but still it seems best to 

 include them. To distinguish at a glance the positive from the 

 negative data, an asterisk is placed before the record of each host 

 in which Opalinids were found. 



Attention is called to the fact that the number immediately follow- 

 ing the name of the host species is, in each instance in which it is 

 found, the United States National Museum catalogue number. 



*3 Some specimens that had been preserved for 85 years were found to contain Opalinids 

 and other Ciliata well preserved. Intestinal worms, also, were found in quite good 

 condition. 



