CYTOLOGICAL INVESTIGATIONS OF COLPODA CUCULLUS GEORGK \V. KIDDKR AND C. LLOYD CLAFF (From the Arnold Biological Laboratory of Brown University and the Marine Biological Laboratory, Woods Hole, Massachusetts) Inasmuch as the various species of Colpoda have interested many previous investigators, especially with regard to factors of encystment and excystment, it was thought worth while to make a careful study of the best known species, Colpoda cucullus Muller. So many interest-ing and hitherto unreported phenomena have been observed that it \\as thought advisable to present only the cytological results in this first report. Subsequent reports will deal with the many and interest-ing observations on other phases of the problem which are at hand and these will be supplemented by further and more complete data. The life histories of various species of Colpoda have been investi-gated from time to time starting with the work of Stein in 1854. He reported the encystment of Colpoda cucullus, the subsequent division into two, four, eight and even sixteen smaller individuals and their ultimate escape from the ruptured cyst. Rhumbler (1888) made an extended study of the process of encystment and division in Colpoda cucullus and C. steini and distinguished between the division cysts, 'Theilungscyste," and those cysts within which division does not occur, the permanent cysts, " Dauercyste." He describes in some detail the appearance and activity of freshly encysted and dividing forms, noting that the cilia are retained throughout the division process but are lost during their stay in the permanent cysts. He observed quite accurately the gradual loss of the food inclusions, during perma-nent cyst formation, although his interpretation of the method of this loss is open to serious question. \\Vnyon (1926) has given a rather diagrammatic account of the division of Colpoda steini, agreeing with the accounts of Stein and Rhumbler but adding some details of the nuclei. Wenyon's observa-tions were made on fixed and stained material while those of Stein and Rhumbler were mostly obtained from the living material. Very recently Penn (1U37) has reported the occurrence ot binary and quadruple division without encystment in a strain of Colpoda cucullus. Kncystment before division occurred in his race only when the cultures were old or when the cultures became crowded. He was 178
BioStor
