PROCEEDINGS OF THE UNITED STATES NATIONAL MUSEUM 



issued iMrfjNvA. Slf sSi h (fie 



SMITHSONIAN INSTITUTION 



U. S. NATIONAL MUSEUM 



Vol.87 Waihington: 1940 No. 3077 



FURTHER STUDIES ON THE OPALINID CILIATE 

 INFUSORIANS AND THEIR HOSTS 



By Maynaed M. Metcalf 



INTRODUCTION 



This paper should be read in connection with "The Opalinid Ciliate 

 Infusorians," U. S. National Museum Bulletin 120, 1923, of which it is 

 really a revision and a second part. About 30 new species and sub- 

 species are described; species described by others since 1923 are con- 

 sidered and illustrations and measurements copied; the taxonomy of 

 the family is reviewed, as well as the data and hypotheses as to geo- 

 graphic distribution; and former reviews of the literature (Metcalf, 

 1909 and 1923a) are brought to date. Thus, Bulletin 120 and the 

 present paper together cover the family Opalinidae as now known. ^ 



The whole body of data as to geographical distribution of the para- 

 sites and the hosts is discussed in an attempt to answer a number of 

 questions as to, e. g., place of origin of each of the several families, 

 subfamihes, and some of the genera of Anura; the geologic period of 



I The cytology of the opalinids described in the present monograph has not been studied in detail. The 

 author welcomes and cordially subscribes to the findings and conclusions of his friend Dr. T. T. Chen, who, 

 in a series of studies, has described the behavior of opalinid chromosomes during mitosis in greater detail 

 than has been done previously. Dr. Chen has demonstrated for the first time for the opalinids the following: 

 (1) Individuality of chromosomes; (2) diploidy; (3) the relation between chromosomes and nucleoli; (4) 

 that the so-called "macrochromosomes" described by other investigators are not chromosomes or a distinct 

 set of chromosomes different from the ordinary kind but parts of certain chromosomes; (5) that the so-called 

 "midmitotic resting stage" described by other investigators is a misinterpretation, the nucleoli in the resting 

 nucleus having been considered as chromosomes. These phenomena had escaped observation or proper 

 interpretation by other workers, though some of them were working in the best laboratories for protozoan 

 cytology. I have seen Dr. Chen's preparations, and I am very glad of this opportunity to refer to the 

 skill and accuracy of his beautiful studies, which place the cytology of the opalinids on a new and sound 



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