OPALINID CILIATE INFUSORIANS — METCALF 481 



seems to be that B. maxima is the most ancient of the four hosts and 

 .that its two closely similar Protoopalinas show an early condition of 

 evolutionary divergence. In B. orientalis, during its wandermg to 

 its present home near the base of the Korean Penmsula and during its 

 subsequent residence there, the two Protoopalinas, probably already 

 present, diverged still farther to give the now very distmct species 

 P. macrocaudata and P. orientalis. Two Bombinas, or perhaps their 

 common ancestor, wandered north from southwestern China and 

 turned westward to reach Europe. During this extensive period of 

 migration and of residence in the west, the species evolved into two, 

 one, B. igneus, now living in the low country, the other, B. pachypus, 

 living among the hills, although their habitats overlap. B. igneus 

 breeds usually in larger pools of still water or in sluggish streams, 

 while B. pachypus is more likely to lay its eggs in small, perhaps 

 transient, pools, even in puddles in wheel ruts. Probably as a result 

 of their overlapping habitats and the consequent at least occasional 

 common breeding pools, the two hosts still carry the same two species 

 of Protoopalina. If the altitude preferences of the two species of 

 Bombina should become more sharply distinct, causing them to breed 

 always in separate pools, B. igneus only at low altitudes, B. pachypus 

 only at higher altitudes, opportunity would be given for evolution 

 to develop in each host its own distinctive two species of parasites, 

 as has occurred in B. orientalis. 



Measurements, in microns, of Protoopalina yunnanensis cheni: 



Measurement 



Length of bodv 



Width of body 



Length of daughter nuclus 



Width of daughter nucleus 



Length of cilia 



Interval between lines of cilia, anterior. 



400 



83 

 52 

 20 

 24 

 1.3 



450 

 90 

 43 

 21 



250 



PBOTOOPALINA LIMNOCHARIS Nie 



Figure 36 



Host: Rana limnocharis Gravenhorst, from Nanking, China. 



Body is rather flattened and about 10 times as long as broad. The 

 greatest width is at a region a Httle anterior to the middle of the body, 

 and from there the body tapers very gradually toward the ends. 



The two pear-shaped nuclei are connected by a long thread. The 

 anterior nucleus is situated at about the anterior sixth, while the 

 posterior one lies a little anterior to the middle part of the body. 

 Each nucleus contains about 10 nucleoH of different size and shape 

 and irregularly disposed. 



166877—40 2 



