THE OPALINID CILIATE INFUSORIANS. 



43 



figure 20 are less slender forms. In figure 18 the animals are con- 

 siderably more stocky and do not taper gradually to the j30sterior 

 tip. Figure 17. h, shows individuals almost as stoek}^ as extreme 

 caudata lata such as are drawn in figure 17, a. 



Some of these intermediate forms of P. caudata closely resemble 

 P. intestinalis, but the infections can be distinguished by the smaller 

 size of the individuals ; by the fact that many bear posterior " spines " 

 and others are at least sharply pointed posteriorly; and especially 

 by the fact that in these, as in all forms of P. caudata, the number 

 of massive chromosomes is six (figs. 18, e and 19, e), while in P. in- 

 testinalis there are eight (figs. 3 and 4, d). Protoopalina caudata, 

 with its diverse forms, well illustrates the danger of specific descrip- 

 tion of Opalinids from limited material. Yet in this paper numer- 



i^iG. 20. — Protoopalina CAUDATA, from Bombixa pachypa ; bach grodp was taken 



FROM A SEPARATE HOST. X 117 DIAMETERS. THESE ANIMALS INTERGRADB BETWEEN TUB 

 FORMS ATTENUATA AND LATA. THE ANTERIOR ENDS ARE ABOVE IN ALL FIGURES EXCEPT 

 THE THIRD IN THE UPPER LEFT-HAND GROUP. 



ous species must be described and named on the basis of one or only 

 a few infections. 



I do not see that we have data to indicate the interpretation of the 

 broad and narrow forms in this species. There seems nothing to 

 show that the narrow individuals give rise to males and the broad 

 individuals to females, nor are there observations to associate the 

 narrow animals with a preponderance of longitudinal division and 

 the broader animals with an especial prevalence of transverse fission. 



Specimens of these intermediate forms have been deposited with 

 the United States National Museum as Cat. No. 16434. 



PROTOOPALINA CAUDATA DISCOGLOSSI, new subspecies. 



Type — United States National Museum Cat. No. 16438. 

 Host. — Discoglossus pictus Otth ; two infections, a, in United 

 States National Museum specimen No. 10052 from Sardinia, the type 



