842 GENERAL METABOLISM [pt. in 



red, which showed that the internal pH was between 5 and 6, with 

 an average of about 5-5. No change appeared after fertiHsation, and 

 eggs in segmentation stages gave the same results as the unfertilised 

 ones. Cytolysis, according to Vies, led to a rise in pH, the dye at 

 the edge of the cell becoming purple or blue, instead of yellow, a 

 phenomenon which he attributed to loss of carbon dioxide. At the 

 same time, Reiss published a paper on the internal />H of the nucleus 

 as distinguished from the cytoplasm. Included in it were various 

 determinations by the microcompression method on other eggs, 

 which gave results as follows : 



For the comparative measures on nucleus and cytoplasm he used 

 the almost transparent eggs of Echinocardium cordatum before they lose 

 their germinative vesicles. He reported that he found the nucleus to 

 take on a deep mauve colour with bromcresol purple, while yet the 

 cytoplasm was distinctly yellow. Bromthymol blue coloured the 

 cytoplasm yellow, the germinative \'esicle yellowish green, and the 

 nucleolus bluish green. The same effects were seen with the unripe 

 eggs oi^ Strongylocentrotus and Sabellaria. Reiss stated that, although the 

 cytoplasm of the egg-cell remained fairly constant with respect to 

 the pa of the external medium, the nucleus was markedly affected 

 by it, and its pH varied in harmony with it. The experiments which 

 supported this view were done on the eggs of Psammechinus milearis 

 and Echinocardium, but they have never been confirmed. Complicated 

 results were also found to follow when anaesthetics were used, but 

 these also have not been repeated, and need not be discussed. 



Later, Reiss made a special study of the changes in internal pH 

 taking place in the echinoderm egg during cleavage. He used an 

 apparatus by means of which half the field of the microscope was 

 made to correspond to variable pH indicator tints by means of a 



