STRUCTURE AND DEVELOPMENTAL RATE 235 



There is also a possible chemical interpretation of the limited 

 moment. The great activity and high oxidation rate of a given 

 group of cells might result from the formation of certain specific 

 compounds of a highly labile nature within these cells. Should 

 the available oxygen be insufficient or the temperature be too 

 low at the moment of origin of such molecules, they would be 

 unable to produce the usual cellular activity, and on account of 

 their labile nature would soon become changed. The oppor- 

 tunity for unusual growth activity of the specific kind on the part 

 of the given cellular group would be lost. No doubt some such 

 peculiar chemical process must be taking place during the different 

 stages of cellular growth and differentiation in a complex ver- 

 tebrate embryo. When such labile compounds do break down 

 we may also imagine that a more generalized chemical condition 

 of the cell is produced. And such cells may subsequently take 

 part in the formation of the more general tissues and may not nec- 

 essarily be lost on account of not having succeeded in giving rise 

 to the specific tissue intended. Certainly, one does not find 

 necrotic and disintegrating cells in all brains of anophthalmic 

 embryos. 



Ralph Lillie ('17) has described structures simulating organic 

 growths arising from electrolytic local action in metals. He also 

 shows the formation of filaments from one metal to be inhibited 

 by contact with another metal. ''The inhibitory influence of 

 zinc upon the formation of ferricyanide filaments from iron may 

 be shown as follows: a straight piece of thin bright iron wire 

 some centimeters long, one end of which is w^ound with a small 

 strip of zinc, is placed in a 2 per cent Kr-FeCye solution in dilute 

 egg-white. Filaments put forth rapidly from the zinc, especially 

 near the iron, but the iron itself remains perfectly bright and 

 bare, and may show no development of filaments for hours. If 

 then the wire be cut in two by scissors, the part remaining in 

 connection with the zinc remains unchanged, while the isolated 

 part quickly develops the characteristic blue-green filamentous 

 growth of ferrous ferricyanide. Evidently this growth had previ- 

 ously been repressed by the influence of the zinc . . . ." 

 Or when the zinc becomes completely covered by a growth of 

 zinc ferricyanide the growth of ferrous ferricyanide will begin. 



