ON SOME PHYSICAL MANIFESTATIONS OF LIFE 63 



brought back into normal sea water, they break apart into from six 

 to sixteen cells simultaneously in about ten or twenty minutes after being 

 put back into normal sea water. If they remain for five or six hours 

 in the hypertonic solution, many eggs suffer. If they do not suffer 

 they soon break up, when put into normal sea water, into a still larger 

 number of cells than if they remained only for three or four hours in 

 the hypertonic sea water. I have seen such eggs divide simultaneously 

 into about forty cells, or more, in from ten to twenty minutes after 

 being put back into normal sea water. These phenomena of segmen- 

 tation are accompanied by violent phenomena of streaming or proto- 

 plasmic motion at the surface of the egg. From these facts I concluded 

 that while the hypertonic sea water inhibits the cell division, it allows 

 the division of the nucleus, which precedes the segmentation of the 

 protoplasm.* W. W. Normanf undertook a histological examination 

 of the eggs under these conditions. He found that if the concentra- 

 tion of the sea water be adequately, but not excessively, raised through 

 the addition of a definite amount of NaCl, KCl, or MgCl^, the nuclei 

 of the eggs divide in the hypertonic sea water karyokinetically, into 

 two, four, and eight successively, while no cell division occurs. When 

 such an egg with eight nuclei is put back into normal sea water, 

 it divides as a rule into more than eight cells simultaneously. If a 

 slightly too high concentration is used, the distribution of the nuclei 

 in the egg does not become so regular; if the concentration is still a 

 little higher, an excessive number of astrospheres is formed, as Morgan 

 and Norman found. In this case, the nuclear material is often not 

 scattered in the egg, although the nucleus seems to be broken into smaller 

 fragments, for if brought back into normal sea water such eggs break 

 up rapidly into a larger number of cells. R. Hertwig had already 

 observed the formation of astrospheres in the unfertilized eggs of the 

 sea urchin when he added a Uttle sulphate of quinine to the sea water, 

 and Morgan appHed the method used by myself and Norman to the 

 unfertilized egg and found an excessive number of astrospheres, just 

 as Norman had observed in the fertihzed egg.J 



It is obvious from these and other experiments not mentioned here 

 that the loss of water on the part of the fertilized egg ultimately retards aU 

 the phases of nuclear and cell division, but not all quantitatively alike. 

 It seems that the chemical process of transformation of protoplasmic into 

 chromatin material is less interfered with than the cell division proper. 

 This follows from the fact that the chromosomes may divide without 



* Loeb, /««>•. of Morphology, Vol. 7, p. 253, 1892. 



f W. VV. Norman, Archiv fur Entwickelungsmechanik, Vol. 3, p. 106, 1896. 



j Morgan, Archiv fur Entwickelungsmechanik, Vol. 8, p. 448, 1899. 



