PLATE LII. 



Effects of Carbonic Acid. 



Eggs in 1-8-cell stage left for 28 hrs. in sea water £ saturated with CO*. 

 Fig. 119. Exp. 1163: Egg showing the individually distinct chromosomal 



divisions; also the cell membrane separated 



• )ll 



substance 



Fig. 120. Exp. 1163: Eggs showing five protoplasmic cells (one of them with 



unsegmented 



Fig. 121. Exp. 1164: Side view of an egg similar to the preceding. 



Fig. 122. Exp. 1163: The second polar body is abnormally large; an accessory aster (S) lies in the yolk- 



of the nucleus in the 1st cleavage has taken place normally, though the spheres are prevented 



from moving to their normal positions above the nuclei by the presence of the large polar body 



furrow cuts into 



cleavage head 



Fig. 123. Exp. 1163: The C and D quadrants are entirely normal 



eggs 



divided but the cell did not; these two nuclei in an undivided cell gave off a single blastomere of the first 

 set (lab) with large tabulated nucleus, the nuclei, spheres and cytoplasmic areas of the cell AB then came 

 to lie at opposite sides of the macromere and each divided independently giving rise to a second micromere 

 (2a, 26) which is nearly normal. 



Fig. 124. Exp. 1163: There are three macromeres one of which contains a perfect spindle but no 

 chromatin; another contains a polyaster and has given off a large micromere with three nuclei; the third 

 contains a single nucleus which is smaller than normal and has given off in reversed cleavage a 1st and a 2d 

 micromere, the former of which is dividing. 



Fig. 125. Exp. 1163: The first cleavage furrow failed to appear though the nuclei divided; at the 2d 

 cleavage each nucleus with its adjacent oSplasm gave off a smaller macromere (B and D), leaving macromeres 

 A and C still undivided ; each of these four macromeres has given off a micromere of the 1st set. 



Fig. 126. Exp. 1163: Three macromeres one of which contains several centrosomes and spheres 

 (S) but no nucleus; another contains a bifurcated spindle and a normal one and has just given off two micro- 

 meres one on the right and one on the left ; the other macromere contains a single nucleus and sphere and has 

 just given off a micromere on the right; two large micromeres with abnormal nuclei occupy the center of 

 the micromere field. There is a general resemblance of this egg to that shown in fig. 124. 



Fig. 127. Exp. 1163: Side view of egg with two macromeres and several micromeres. Strands of 

 protoplasm run from the polar bodies to the micromeres and from one of the latter to a macromere, sug- 

 gesting the "spinning" activities of other eggs; lobes are also found on several cells. 



Fig. 128. Exp. 1163: Two macromeres, each with two nuclei and two or more spheres; in the second 

 cleavage the nuclei divided but the cell-body did not; in the third cleavage there was probably a triaster 

 in each macromere, since only two micromeres of the first set were formed (lab, led) each with multiple 

 nuclei; in the fourth cleavage each macromere contained two separate spindles and gave off two separate 

 micromeres (2a, 26, 2c, 2d) of the second set; the nuclei in the macromeres are so well separated that it is 

 probable that at the next cleavage two independent spindles would form in each macromere and would 

 lead to the formation of four micromeres of the third set. 



nse 



Fig. 129. Exp. 1163: Macromeres A and B did not separate at the 2d cleavage, but each has given 



to three micromeres forming a typical micromere plate, though the direction of division in A and H 

 has sometimes been atypical. 



Fig. 130. Exp. 1164: Irregular cleavage mass in which it is not possible to identify many cells. 

 Several of the cells show loose membranes and lobes. 



Fig. 131. Exp. 1163: One of the macromeres (D) was separated from the other three, but each has 

 given rise to three micromeres which have subdivided in normal manner, the micromeres formed from 

 lying on the right of the micromere Dlate formed from the other macromeres. 



