156 PATTERNS AND PROBLEMS OF DEVELOPMENT 



Still another series of determinations of oxygen uptake in pieces from 

 Amhly stoma and Rana embryos" shows the dorsal lip region much higher 

 than the ventral lip and slightly higher than the presumptive epidermis, 

 but Barth points out that the cells of the dorsal lip contain more yolk 

 than those of the epidermis; consequently, intensity of respiration in the 

 metabolizing protoplasm of the dorsal lip must be considerably higher 

 than appears from the data. On the ventral side oxygen uptake decreases 

 basipetally from the apical region. 



Somewhat earlier, glycogen distribution in amphibian embryos was in- 

 investigated by Woerdeman (1933a, h, d). His findings show more or less 

 uniform distribution in the apical hemisphere with decrease in the dorsal 

 lip on invagination. Similar conclusions were reached by Tanaka (1934), 

 and a decrease was also observed on invagination of transplanted pieces 

 of the dorsal lip region (Raven, 1933a, 1935a). Using a different method 

 for demonstrating glycogen, Pasteels (1936c) maintains that the supposed 

 decrease does not occur. However, work with a quantitative microchem- 

 ical method indicates that before gastrulation glycogen decreases basip- 

 etally from the apical pole and that during gastrulation there is decrease 

 in amount in all regions, but that decrease is greatest in the invaginating 

 material (Heatley and Lindahl, 1937). These observations are interesting 

 in relation to the data of Boell, Needham, et al. on glycolysis. 



Most amphibian eggs and embryos are unsatisfactory material for dye 

 reduction because of their pigmentation. Recently, however, some obser- 

 vations have been made on unpigmented or shghtly pigmented forms. 

 Staining the unpigmented neurula of the urodele Triton cristatus by re- 

 oxidation of the leucobase of brilliant cresyl blue and observing reduction 

 under strictly anaerobic conditions, Fischer und Hartwig (1936) found 

 reduction most rapid in the floor of the open neural plate. Using the same 

 material and the same procedure, Piepho (1938) followed the course of 

 reduction in blastulae and gastrulae. In blastulae reduction occurred most 

 rapidly in a region extending from the apical pole almost to the equator 

 and from there progressively to the basal pole. Gastrulae, so far as they 

 gave definite results (60 per cent of the total), showed, like blastulae, 

 more rapid reduction in the region apical to the equator and also in the 

 region of the dorsal lip of the blastopore, the inductor region. Whether 

 one of these regions reduced more rapidly than the other could not be 

 determined. In these experiments reduction occurred under nitrogen, that 



35 Barth, 1939a, h; oxygen uptake in cubic millimeters of oxygen per 100 mg. dry weight 

 per hour. 



