HETEROPLOIDY IX TRITURUS TOROSUS. II. THE INCIDENCE OF CHROMOSOMAL VARIATIONS IN SHIPPED LARVAE 1 DONALD P. COSTELLO AND CATHERINE HENLEY L'uh'crsity of .\ortli t 'itroliini Studies on the incidence of heteroploidy and other cytological abnormalities in salamander larvae have been given considerable impetus in recent years by the \v<rk of Fankhauser and his students. Such studies have been concerned with the experimental production of chromosomal aberrations, as well as with their spon-taneous occurrence in natural populations of amphibian larvae. A general review 7 of the results obtained before 1945 is presented by Fankhauser (1945). The eggs of the California newt, Trititnts torosits, are laid in "clutches" which are available in large numbers near Stanford University. Since no systematic ef-fort had been made to determine the spontaneous incidence of heteroploidy in this form, it was decided in 1947 to undertake such a survey. Accordingly, a number of egg masses were sent by Railway Express from Palo Alto to Chapel Hill, in a thermos jug containing ice and water ; this is the usual method for shipping am-phibian eggs. Cytological examination of the larvae developing from these eggs revealed a high frequency of chromosomal mosaicism and very radical mitotic anomalies. A comprehensive study was begun early in 1948 in order to eliminate the possi-bility that such aberrations might be present in material not subjected to shipment. Tail-tips from larvae fixed in California had only a very low incidence of abnor-mality, suggesting that factors involved in shipment might be responsible for the observed effects. During the period when this control material was being fixed and studied in California, another group of T. forosus eggs was shipped east to Chapel Hill. Egg clutches collected at the same time and in the same locale as these "1948 shipped eggs" were raised under known conditions, so that a specific control for this second group of shipped larvae was available. The data from a study of the control animals have been presented in detail by Costello and Henley (1949). The present paper will describe the results of a study of the original (1947) group of shipped larvae, as well as the second (1948) group. Preliminary reports concerning small random samples of these shipped larvae have been noted in abstracts (Costello and Henley. 1947a, 19471), 1948; Costello, 1948). We are indebted to Dr. Victor C. T witty and Dr. H. E. Lehman for their kind-ness in sending us the original batch of shipped eggs in 1947. 'This work was made possihlr by grants from the American Philosophical Society, and tin-Carnegie and Smith Research Funds of the University of North Carolina.