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INTRODUCTIONThis paper should be read in connection with "The Opalinid CiliateInfusorians," U. S. National Museum Bulletin 120, 1923, of which it is really a revision and a second part. About 30 new species and subspecies are described; species described by others since 1923 are considered and illustrations and measurements copied; the taxonomy of the family is reviewed, as well as the data and hypotheses as to geographic distribution; and former reviews of the literature (Metcalf, 1909 and1923a) are brought to date. Thus, Bulletin 120 and the present paper together cover the family Opalinidae as now known.T he whole body of data as to geographical distribution of the parasites and the hosts is discussed in an attempt to answer a number of questions as to, e. g., place of origin of each of the several families, subfamihes, and some of the genera of Anura; the geologic period of I The cytology of the opalinids described in the present monograph has not been studied in detail. The author welcomes and cordially subscribes to the findings and conclusions of his friend Dr. T. T. Chen, who, in a series of studies, has described the behavior of opalinid chromosomes during mitosis in greater detail than has been done previously. Dr. Chen has demonstrated for the first time for the opalinids the following:(1) Individuality of chromosomes; (2) diploidy; (3) the relation between chromosomes and nucleoli; (4) that the so-called "macrochromosomes" described by other investigators are not chromosomes or a distinct set of chromosomes different from the ordinary kind but parts of certain chromosomes; (5) that the so-called "midmitotic resting stage" described by other investigators is a misinterpretation, the nucleoli in the resting nucleus having been considered as chromosomes. These phenomena had escaped observation or proper interpretation by other workers, though some of them were working in the best laboratories for protozoan cytology. I have seen Dr. Chen's preparations, and I am very glad of this opportunity to refer to the skill and accuracy of his beautiful studies, which place the cytology of the opalinids on a new and sound *""^• 465 466 PROCEEDINGS OF THE NATIONAL MUSEUM vol.87 the origin of each group of these hosts; the routes and the geologic times of the distribution of several groups of hosts; the places and times of origin of the several genera and some of the subgenera of opalinids and the routes and times of their distribution. Paleogeographic hypotheses of Arldt, Haug, Scharff, Schuchert, and others are tested by using them in connection with the distributional data from Anura and opalinids and seeing whether the hypotheses furnish reasonable explanations of the faunal data. The methods of speciation in the opalinids and the general principles of their evolution also are discussed. ACKNOWLEDGMENTS

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Purpose: A paradigm shift in the management of small renal masses has increased utilization of active surveillance. However, questions remain regarding safety and durability in younger patients. Materials and Methods: Patients aged 60 or younger at diagnosis were identified from the Delayed Intervention and Surveillance for Small Renal Masses registry. The active surveillance, primary intervention, and delayed intervention groups were evaluated using ANOVA with Bonferroni correction, c 2 and Fisher's exact tests, and Kruskal-Wallis and Wilcoxon signed-rank tests. Survival outcomes were calculated using the Kaplan-Meier method and compared with the log-rank test.Results: Of 224 patients with median followup of 4.9 years 30.4% chose surveillance. There were 20 (29.4%) surveillance progression events, including 4 elective crossovers, and 13 (19.1%) patients underwent delayed intervention. Among patients with initial tumor size 2 cm, 15.1% crossed over, compared to 33.3% with initial tumor size 2e4 cm. Overall survival was similar in primary intervention and surveillance at 7 years (94.0% vs 90.8%, log-rank p[0.2). Cancer-specific survival remained at 100% for both groups. There were no significant differences between primary and delayed intervention with respect to minimally invasive or nephron-sparing interventions. Recurrence-free survival at 5 years was 96.0% and 100% for primary and delayed intervention, respectively (log-rank p[0.6). Conclusions: Active surveillance is a safe initial strategy in younger patients and can avoid unnecessary intervention in a subset for whom it is durable. Crucially, no patient developed metastatic disease on surveillance or recurrence after delayed intervention. This study confirms active surveillance principles can effectively be applied to younger patients.