April 9. Operated limb a little more massive than normal. April 11. Limb more massive, rounded, not more distinctly marked off posteriorly than anteriorly when viewed from above. Points dorsally slightly posteriorly in lateral view. April 14. More massive, but otherwise normal. April 22. Not quite so long; syndactyly first two digits, otherwise normal. May 4. Normal except for syndactyly. Experiment H. R. E. 9. April 11, 1917. Posterior half left limb bud in place of anterior right (fig. 120, 10). Wound perfectly healed same. evening. April 14. Operated limb bud looks nearly normal. No definite pointing. April 16. Two rather distinct nodules, the posterior one considerably more prominent. April 18. Posterior bud smaller than normal, points dorsolaterally. Anterior one not so definite. April 23. Two entirely separate limbs; anterior one is shorter, points ventroposteriorly; posterior one points straight to side; no digitations. April 28. Two limbs point posterolaterally, parallel to one another; anterior one thicker, has two digits and beginning of third; apparently a normal, though much smaller, right limb in approximately normal position. Posterior limb thinner, rod-like, with no digits. May 4. Anterior limb a normal right; posterior, very imperfect, has one long digit and third digit nodule on upper border; elbow bend shows; limb probably also a right (?) May 12. Anterior limb has good function. May 21. Specimen preserved. The anterior member is a normal right, somewhat smaller than the unoperated limb. Posterior member has one long and one short digit, and has same general position as the anterior. Total view leaves in uncertainty which is palmar surface (fig. 131). Sections show clearly that the ventrolateral surface is the palm and that the limb is therefore a left. Experiment H. R. E. 20. May 2, 1917. Dorsal half left limb bud in place of dorsal right (fig. 120, 11). May 3. Wound perfectly healed. May 7. Operated limb about full size, points anteriorly and slightly dorsally. May 10. Projects straight to side. Slight indication of posterior reduplicating bud from near attachment of limb. May 14. Main limb points dorsolaterally and slightly posteriorly. The reduplicating bud is attached near base and in part directly to body wall; it has grown considerably, but is still without digits. May 18. Main (anterior) member sticks out to side, but now points distinctly posteriorly as well, is slender and with two digits. Other limb shorter, but considerably stouter, with faint indication of two digits. May 27. Anterior member has remained slender, and still has but two digits; distinct elbow bend; general shape indicates it to be a right. The posterior member, practically normal except slightly underdeveloped, is an undoubted right; first two digits partly syndactylous (first short); third is distinct and fourth indicated. Some function in this member. May 28. Specimen preserved; form of limbs shown in figure 132. Sections show that there are two separate sockets in the shoulder-girdle for the two limbs. The medial surface of both is the palm. Hence both are rights. 21. Heteropleural, dorsoventral Experiment H. R. E. 36. April 4, 1918. Ventral half left limb bud (inverted) in place of dorsal right (fig. 120, 16). Pronephros removed. April 5. Perfectly healed. April 8. Operated bud a little sharper; points normally (dorsoposteriorly). April 10. April 13. April 16. Nearly normal; points slightly more dorsally. Normal limb; digitations show. April 30. Specimen preserved (fig. 133). Experiment H. R. E. 10. April 11, 1917. Anterior half left limb bud (inverted) in place of anterior right (fig. 120, 13). Wound completely healed same evening. April 14. Limb bud operated side nearly normal looking. April 16. April 18. April 23. Operated limb normal except slightly larger. April 28. Operated limb a normal right with two digits arising from palmar surface near radial border; arm somewhat thicker than normal. May 7. Specimen preserved (fig. 134). The first digit is somewhat small; the reduplicating digits (DU) are united at base. Vol. 7, No 1, pp. 41-44, January 1921 | THE PRESENT STATUS OF THE LONG-CONTINUED PEDIGREE CULTURE OF PARAMECIUM AURELIA AT YALE UNIVERSITY BY LORANDE LOSS WOODRUFF OSBORN ZOOLOGICAL LABORATORY, YALE UNIVERSITY Communicated by R. G. Harrison, December 30, 1920 As a matter of record it seems advisable to bring up to date and summarize the chief results derived from the writer's main pedigree culture of Paramecium aurelia. This culture, designated Culture I, was started on May 1, 1907, by the isolation of a "wild" individual which was found in a laboratory aquarium.1 The original specimen was placed in about five drops of culture fluid on a glass slide having a central ground concavity, and when this animal had produced four individuals, each of these was isolated on a separate slide to form the four lines of the culture. The four lines have not been kept distinct from one another throughout the work, but have been replenished by cells from one of the sister lines when, through accident or otherwise, one or another of the lines has become extinct. 42 ZOOLOGY: L. L. WOODRUFF PROC. N. A. S. The culture has been maintained by the isolation of a specimen from each of these lines practically every day, with the exception noted below. The number of divisions in each line has been recorded at the time of isolation and the average rate of these four lines has again been averaged for varying numbers of days (5, 10, or 30 days) as the exigencies of the different experiments demanded. These data have afforded the graphs of the division rate. Permanent preparations have been preserved from time to time for the study of the cytological changes during the life history. During the first eight months of the work the culture medium consisted of infusions of hay and fresh grass, but from February, 1908, to the present time various materials collected from ponds, swamps, etc., have been employed. The infusions were thoroughly boiled to prevent the contamination of the pure culture with foreign strains of Paramecium. In short, the cells of the four lines of the culture to-day are direct lineal descendants by division of the single animal isolated in 1907. The object of starting the culture was to determine whether Paramecium can reproduce by division indefinitely without recourse to conjugation. Throughout the work the possibility of conjugation in the four lines of the culture has been precluded by the almost daily isolation of the products of division. Accordingly its continued life and health has long since justified the conclusion that conjugation, involving syncaryon formation, is not, as previously generally maintained, a sine qua non for the continued life of Paramecium, in particular, and, presumably, of Infusoria in general. At the completion of the The figures 1000, 2000, etc., represent generations and are placed above the periods > in which they were attained. culture's first five years of life, during which over 3029 generations were attained, the writer stated that "the organisms of the present generation are in as normal morphological and physiological condition as the original 'wild' individual isolated to initiate the culture. This study has indicated that, under favorable environmental conditions, the protoplasm of the cell originally isolated possessed (at least) the potentiality to produce similar cells to the number represented by 2 raised to the 3,029th power, or a volume of protoplasm not less than 101000 times the volume of the Earth. I believe this result indicates beyond question that the protoplasm of a single cell may be self-sufficient to reproduce itself indefinitely, under favorable environmental conditions, without recourse to conjugation.... As a matter of fact organisms taken from this culture of Paramecium have shown but little tendency to conjugate. From time to time experiments to induce conjugation have been carried out in mass cultures started from the pedigree lines. The first successful experiment occurred in December, 1913, at about the 4100th generation. The next epidemic of conjugation in mass culture occurred June, 1920. 3 Careful studies of the rate of division of sub-lines derived from the main lines and bred under the most constant environmental conditions revealed the fact that there are inherent, normal, minor, periodic rises and falls of the fission rate due to some unknown factor in cell phenomena. These were termed Rhythms. In a search for the underlying factors of rhythms a complicated internal nuclear reorganization process was discovered and named Endomixis. This process involves the periodic formation of a complete new nuclear apparatus by a definite sequence of normal morphological changes which simulate those occurring in conjugation. Endomixis, in essence, consists of a gradual disintegration and absorption of the macronucleus in the cytoplasm. Simultaneously a multiplication of the micronuclei is in progress. Certain of the resulting micronuclei degenerate while the remaining one or two form the new macronuclear and micronuclear apparatus of the cell. This results in the |