110 



5. Studies on Opalina. 



(Preliminary Notice.) 



By Maynard M. Metcalf, Prof, of Zoology, Oberlin, Ohio, U.S.A. 



(From the Zoological Institute Würzburg.) 



(With 7 figures.) 



eingeg. 5. Juli 1907. 



In the Spring of 1900 Mr. Ernst Teichmann, at Prof. Boveri's 

 suggestion, began a study of the cytology and reproduction of Opalina 

 caudata. The study, however, was never completed, though several in- 

 teresting results had been obtained. "When I reached Würzburg, last 

 fall, Prof. Boveri called my attention to the large size and clearness 

 of the nucleus in this species and suggested that I study it. For this 

 suggestion and for constant advice during the course of the work I am 

 very grateful to him. 



Most of Mr. Teichmann's preparations are mislaid and cannot 

 be found. Some of his sections, however, I have used, and lately I have 

 seen his drawings. 



The study of Opalina has proven of much interest. The minute 

 anatomy, especially of the nucleus, has been studied chiefly in Opalina 

 intestinalis and 0. cautata, each of which has but one pair of nuclei. 

 Comparisons have been made with 0. rananim, 0. diì7iìdiata^ 0. obtri- 

 gona and with a new species which I will name 0. zelleri^. Excretory 

 organs have been found in the two binucleate species in 0. obtrigo?ia, 

 0. dimidiata and doubtfully also in 0. xelleri. These have been described 

 in a paper now in press (Arch. f. Protistenkde.). The processes of re- 

 production, which occur in the spring, have been followed in the two 

 binucleated species and in 0. dimidiata. Infection experiments have 

 been made with all the species named except 0. ranarum and 0. xelleri. 

 I will report very briefly upon some of the results of this study. 



Mitosis. 



Opalina intestinalis. 



The nuclear membrane never disappears during division. But re- 

 mains intact, becoming dumbbell-shaped and finally separating into two 

 parts, one for each daughter nucleus. These are connected for a long 

 time by a slender thread, the attenuated membrane. The nuclear mem- 

 brane is very firm. In nuclei which have been removed from the cell 



1 This in the species which Zeller found occurring with 0. dimidiata in Rana 

 esculenta. He thought it very likely a new species, but did not name it. To his de- 

 scription, which is sufficient for diagnosis, I will add a few points in a later publi- 

 cation. 



