INDEX OF SUBJECTS 



Ultra-microscope, 59 

 Ultra-microscopic organisms, 356 

 Ultra-violet light, 20 



effect of, on egg of Nereis, 

 218,341-344, 34^347 

 Unicellular organism, 35, 249 

 Union of egg- and sperm-nuclei, modes 

 of, 179 ff. 



V 



Viscosity, 44-46 



Vitalism, 14 



Vitelline membrane, 140 



W 



Water, component in vital reactions, 

 125 

 distribution of, during cleavage, 



330-331 

 in cells, 41 



movement into and out of cells, 



139 



structural part of living system, 

 124 



Water-drops, 126, 132 



and protoplasmic structure, 137 

 effect of temperature in producing 



them, 136 

 formed by ultra-violet light, 136 

 hypertonic sea-water and, 136 

 in normal eggs, 137 

 in nucleus, 134 

 rate of formation of, 134 

 rhythmical phenomenon, 137 



Water-level in cells, 143, 243-245 



White blood cell, 365 



X 



X-ray spectroscopy, 39 

 Y 



Yolk, S3, 54 



role of, in development, 54-55 

 Yolk-spheres, fusion of, 131 



polyphasic, 55 



Zygote nucleus, 164 



392 



