266 SUMMARY OF CURRENT RESEARCHES RELATING TO 



•• immortality." The pedigreed race was kept going Fur seven years, 

 with a generally uniform division-rate, subject, however, to occasional 

 and periodic fluctuations or rhythms. These correspond roughly to 

 what Calkins lias termed cycles, which end in depression periods and, 

 unless stimulated, in death. In rhythms, however, Woodruff maintains 

 that there is no evidence of depression. During the low periods of the 

 division-rate rhythms there takes place, in P.aurelia,a complete nuclear 

 re-organization (endomixis), after which there is renewed vigour. 



The re-organization without conjugation is closely similar to that 

 which follows conjugation, and Calkins points out that there cannol be 

 a great difference in the syncaryon resulting; from the union of two 

 closely related individuals and the functional micronucleus which under- 

 goes asexual endomixis. The terms asexual endomixis and sexual 

 endomixis may serve to distinguish the process of intermingling during 

 parthenogenesis and after conjugation, respectively. Asexual endomixis 

 in Paramecium is parthenogenesis and nothing more. 



Woodruff and Erdmann conclude from their observations that old 

 age and natural death do not occur in Paramecium, and that the so-called 

 cycle is non-existent. Calkins draws the opposite conclusion that the 

 one apparent exception among pedigree races, to the rule of depression and 

 natural death in the absence of conjugation or its equivalent, is now 

 removed, and that Woodruff's culture is no more than a long series of 

 cycles, meaning by a cycle a more or less periodic alternation of high 

 and low vitality as measured by the division-rate. Woodruff's " rhythm" 

 is the same as Calkins's " cycle." 



Calkins concludes : (1) that conjugation or its equivalent has 

 primarily the result, as Biitschli suggested, of offsetting and overcoming 

 the progressive weakening of vitality in Infusorians ; (2) that more or 

 less definite cycles of vigour and depression, ending in natural death 

 unless conjugation or its equivalent supervenes, are characteristic of all 

 pedigreed races of Infusorians ; (3) that physical " immortality " is true 

 of Paramecium and other ciliates only in the same sense that it is true 

 of Metazoa ; and (4) that the protoplasm of Paramecium is subject to 

 the same laws of physiological usury that apply to Metazoa, and 

 undergoes phenomena which, in Metazoa, we call old age, ending in 

 natural death unless conjugation, or its equivalent parthogenesis, saves 

 the race. 



Chromosomes in Opalina.* — Maynard M. Metcalf describes Opalina 

 antilliensis sp. n. from the rectum of the large toad, Bufo agua of 

 Jamaica. It is a binucleated much-flattened form, with spiral lines of 

 cilia. There may be forty-eight lines of cilia at the anterior end, but 

 the number varies with size. The nuclei are more nearly central than 

 in most binucleated forms. In early stages of mitosis the long axes of 

 the nuclei lie nearly transverse to the lines of cilia ; later on they come 

 to lie more nearly parallel to them 



The author discusses the chromosomes in Opalina. They are par- 

 ticularly clear in the new species, where two distinct sets occur, one 

 massive and the other granular. The massive chromosomes occur in. 



* Zool. Anzeig., xliv. (1914) pp. 533-41 (21 figs.). 



