MORPHOGENESIS AND METABOLISM O F AbIPHIBIAN LARVAE AFTER EXCISION OF HEART

In the previous paper of this series (Remp, '53) it was reported that tadpoles of Rana pipiens would live up to 6 days at room temperature after excision of heart at Shumway stage 22 or 23. Because of the obvious differences between anuran and urodele larvae in form and rate of development, the experiment was repeated on Amblystoma punctatum at Harrison stage 40, 41 o r 42 (Kemp and Quinn, '51). It was interesting to find that heartless larvae of Amblystoma survived at room temperature up to 15 days -more than twice as long as tadpoles of Rana. Although there are many similarities in differentiation of circulationless larvae of Rana and Amblystoma, e.g., microcephaly, collapse of the vitreous chamber of the eye, swelling of pronephric tubules, postcardinal sinuses and dorsal mesentery, reduced motility and slow utilization of yolk, there are also important differences. Lymph spaces in the body wall, in which fluid may accumulate, are pronounced in Rana but negligible in Amblystoma. Anterior limb buds and balancers, on the other hand, are present in Amblystoma but absent in developing tadpoles.