PLATE LIX. 

 Effects of Hypertonic Sea Water. 



Eggs represented in figs. 209-218 were in the 2-cell stage when the experiments began, and in none of 

 them did the yolk undergo any subsequent cleavage; figs. 219-223 were in the 4-ceIl stage at the beginning 

 of the experiment. 



Fig. 209. Exp. 865: 4 per cent. NaCl, 2 hrs., normal 10 hrs.; the nuclear division at the 2d cleavage 

 occurred regularly but the cell division was suppressed, thus leaving two nuclei of normal appearance, in 

 each cell; at least three spheres are present in the left cell. 



Fig. 210. Exp. 804: 1 per cent. NaCl, 4 hrs.; partial suppression of the 2d cleavage furrow which is 

 limited to a shallow furrow on the animal pole side of the egg; the nuclei are irregular and densely chromatic. 



Fig. 211. Exp. 864: 3 per cent. NaCl, 3 hrs., normal 10 hrs.; the 2d cleavage spindles have the position 

 of the 3d cleavage spindles of normal eggs; the chromosomes are scattered abnormally on the spindles. 



Fig. 212. Exp. 865: 4 per cent. NaCl, 2 hrs., normal 10 hrs.; the two macromeres have each given 

 off a first and a second micromere, the first by dexiotropic and the second by Isotropic division, as in normal 

 eggs. Each of the first micromeres contain a single nucleus and sphere; the second micromeres and the 

 macromeres contain several spheres and karyomeres or groups of chromosomes. 



Fig. 213. Exp. 863: 2 per cent. NaCl, 2} hrs., normal 10 hrs.; the first set of micromeres have been 

 formed in dexiotropic direction, as in normal cleavage; the macromeres are dividing again with double 

 spindles or tetrasters. 



Fig. 214. Exp. 846: 4 per cent. MgCl 2 , 4 hrs., normal 16 hrs.; the two macromeres are separated by a 

 group of micromeres which have formed along both sides of the 1st cleavage plane; the polarity of each half 

 thus appears to have been changed, the centers of the ectodermal pole being the surface of contact between 

 the two halves; this may be due, in part, to the outward rotation of the macromeres at the vegetal pole 

 and their inward rotation at the animal pole. 



Fig. 215. Exp. 846: 4 per cent. MgCl 2 , 4 hrs., normal 16 hrs.; side view of an egg with two macro- 

 meres and six micromeres; the two original micromeres of the first set have subdivided as indicated by the 

 arrows, the other two micromeres are of the 2d set; all the micromeres contain karyomeres; the macro- 

 meres contain chromosomes scattered apparently, along the line of the 1st cleavage spindle. 



Fig. 216. Exp. 846: Egg from same experiment as the preceding; the nuclei at the vegetal pole are 

 probably derived from chromosomes which were scattered along the first cleavage spindle as in fig. 215. 



Fig. 217. Exp. 822: 2 per cent. NaCl, 16 hrs., normal 8 hrs.; irregular and unequal 2d cleavage with 

 several karyomeres of varying size in each cell. 



Fig. 218. Exp. 842: 4 per cent. MgCl 2 , 5 hrs., normal 17 hrs. ; the divisions of the cell body at the 2d 

 cleavage were suppressed in the left half, but two micromeres are arising in normal manner from this half; 

 several accessory asters are present in this half which have served to scatter the chromosomes. The right 

 half of the egg is quite normal. 



Fig. 219. Exp. 867: 8 per cent. MgCI 2 , f hr., normal 6 J hrs.; the 3d cleavage was very irregular and 

 has given rise to a large number of karyomeres, and spheres which are in division in three quadrants of 

 the egg. 



Fig. 220. Exp. 972: 2 per cent. NaCl, 16 hrs., normal 24 hrs.; second quartet formation; karyomeres 

 or polyasters in each of the cells. 



Fig. 221. Exp. 814: 2 per cent. NaCl, 1 hr., normal 17 hrs.; second quartet formation; karyomeres 

 and spheres in every cell. 



Fig. 222. Exp. 828: 1 per cent. NaCl, 2 hrs., normal 6J hrs.; second quartet formation; karyomeres 

 and polyasters in every cell. 



Fig. 223. Exp. 972: 2 per cent. NaCl, 16 hrs., normal 24 hrs.; karyomeres (and asters) in every 

 cell; all nuclei are vesicular and contain achromatin as well as chromatin. 



