1921, xviii, pp. 240-241. 119 (1701) The early effects of conjugation on the division rate of Spathidium spathula. By LORANDE LOSS WOODRUFF and HOPE SPENCER. Conjugation occurred readily in a pedigree culture of Spathidium spathula and therefore experiments were started to determine the effects of fertilization in the life history of the organism. During the first six months of the work, more than sixty lines were derived directly or indirectly from the parent line by conjugation. Some of the exconjugant lines studied represent the F1, F2, F3, and F1 generations. All the lines which are compared were bred under identical cultural conditions. A comparison of the number of generations attained by each exconjugant line with that attained by its parent line during the first 15 days after the former's origin gives the following results. Forty-two exconjugant lines produced more generations, eight produced less generations and two produced essentially the same number of generations as their respective parent lines. The various cases in which the parent line did not survive the first fifteen days after the exconjugant line was derived from it are not comprised in these data. If such cases were included it obviously would increase the number of plus cases of exconjugant lines. Analysis of the data thus far obtained inevitably leads to the conclusion that the exconjugant lines of this pedigree culture of Spathidium, under the conditions of the experiment, exhibit, in the great majority of cases, a higher division rate for the first fifteen days after conjugation than the parent lines. The evidence to date also indicates that exconjugant lines which are derived from old parent lines (i.e. from lines which have undergone many generations since conjugation) show a relatively greater increase in the division rate, during the first fifteen days, as compared with the parent lines, than do exconjugant lines which are derived from young parent lines (i.e., from lines which have more recently conjugated). The complete paper will appear in the Journal of Experimental Zoölogy. cine, 1921, xviii, pp. 303–304. 156 (1738) The survival value of conjugation in the life By LORANDE LOSS WOODRUFF and HOPE SPENcer. [From the Osborn Zoological Laboratory, Yale University.] In a former communication it has been shown that in our pedigree cultures of Spathidium spathula, exconjugant lines, in the great majority of cases, exhibit a higher rate of division during the first fifteen days than the parent lines.1 The purpose of the present paper is to summarize briefly the results to date with respect to the effects of conjugation as exhibited later in the life history of the pedigree lines. 1. Conjugation in the majority of cases increases the length of life of the exconjugant line, so that it lives after the death of the parent so-called "non-conjugant" line. This is shown by the fact that of forty-seven exconjugant lines, thirty lines lived longer; four lines lived to essentially the same date; and thirteen lines died before their respective parent lines. 2. The total number of generations attained by the exconjugant exceeds those attained by the parent from the date when the exconjugant arose to the death of the parent in about eighty per cent. of the lines. Of fifty-two comparable lines, forty-one lines exceeded their respective parent lines in number of fissions; two practically equalled; and nine lines did not attain so many generations. The fact is evident that conjugation increases the number of fissions to a total which could not otherwise have been reached. 3. If the period be considered during which both lines were alive, the results are even more conclusive. Forty-four lines at 1L. L. Woodruff and Hope Spencer, PROc. Soc. Exp. Biol. and Med., 1921, xviii, 240-241. tained more generations than the parent; four equalled the parent; and four completed a smaller number of fissions. Thus over eighty per cent. of the exconjugant lines attained more generations than their respective parent lines. 4. By analysis of the data from an entirely different angle the same general conclusion is apparent. The total number of generations attained before the F1 generation appeared, plus those from the F1 to the origin of the F2, and so on to the F, generation; amounts to date to from 450 to 550 generations, according to the series followed. The first line reached 234 generations without conjugation, therefore by conjugation it thus far has been possible more than to double the number of fissions obtainable without conjugation. In brief, all the data thus far secured indicate that in this pedigree culture, under the conditions of the experiment, the survival value of conjugation in the majority of cases is markedthe exconjugant lines exhibiting a higher division rate and outliving the non-conjugant lines. The complete paper will appear in the Journal of Experimental Zoology. |