444 BULLETIN 120, UNITED STATES NATIONAL MUSEUM. 



adult Opalinids. To produce a permanent infection tadpoles must 

 ingest cysts. Brumpt regards Protoopalina caudata as a variety of 

 P. mtestalinis [the two forms seems to me better treated as distinct 

 species] . 



Metcalf (1918,a) read before the American Society of Zoologists 

 a paper, an abstract of which was published, as follows : " Opalina 

 and the origin of the Ciliata. Opalina characters, 1, reproduces by 

 both longitudinal (Flagellata) and transverse (Ciliata) fission; 2, 

 sexual act complete fusion of dissimilar gametes (Flagellata) ; 3, no 

 kinetic center (centrosome [unique] ) ; 4, kinetoplasm in form of basal 

 granules of the cilia and a network of neural fibrillae connecting these 

 (Ciliata) ; 5, uninucleate at sexual period, pleurinucleate during tha 

 rest of the life cycle [unique] ; 6, in pleurinucleate condition all nuclei 

 alike ; 7, in each nucleus trophochromatin and idiochromatin digtinct 

 (except in origin) ; in the binucleate species the trophochromatin is in 

 massive chromosomes of constant, definite form and number, appar- 

 ently equal in number to the granular idiochromosomes, and their 

 division in mitosis is regular ; in the multinucleate species the tropho- 

 chromatin masses are not constant in number, size, or form, and may 

 divide irregularly in mitosis ; the trophochromatin is extruded from 

 the nuclei at the sexual period ; 8, the pseudopleurinucleate condition 

 is due to temporary suppression of the divisions of the body, the 

 nuclei having divided; 9, this delay in completion of mitosis affects 

 also the nuclei, which in numerous species do not complete their divi- 

 sion promptly, but come to " rest " in different stages of the incom- 

 plete mitosis. In the 60 ( ?) species studied, 40 (?) of them new [this 

 now proves to be 152± and 137±], a complete series is seen from 

 uninucleate forms with single nucleus in an anaphase of mitosis, 

 through uninucleate \i. e., with two daughter nuclei still connected] 

 species with telophase nuclei, binucleate species with resting nuclei 

 of the usual type, binucleate species with two prophase nuclei, still 

 others with two telophase nuclei, quadrinucleate species, multinu- 

 cleate species, and finally an elongated multinucleated species whose 

 transverse body divisions have started but are arrested while incom- 

 plete, giving an appearance of metamerization. The binucleate 

 Opalinids form a genus, Protoopalina [now divided into two genera, 

 Protoopaliim and Zelleriella], distinct from the multinucleate 

 species, Opalina proper [now Cepedea-\- Opalina'], the chief dis- 

 tinctions being in nuclear characters. The Opalinidae are an off- 

 shoot from the primitive Ciliata before the latter had acquired true 

 binuclearity and the subsequent dimorphism of nuclei. They should 

 be classed as Protociliata, under the Ciliata. The Astomata [other 

 "Astomata"] {Discophrya, Anoplophrya, Hoplitophyra, etc. ?) are 

 Euciliata, having arisen later, after the dimorphic nuclei were ac- 

 quired. They are not closely related to the Opalinidae? 



