572 



CELL DIVISION IN EGGS OF CREPIDULA. 



X. Effects of Hypertonic Sea Water. 

 1. NaCl Added to Sea Water. 



804 

 805 



806 



807 



808 

 809 



810 

 811 



813 



814 



816 

 821 



822 

 823 



824 



Stage. 



1-4 cells. 

 1-4 cells. 



1-4 cells. 



1-4 cells. 

 1-2 cells. 

 1-2 cells. 



1-4 cells. 



1-2 cells. 



1-20 cells. 



1-20 cells. 



1-20 cells. 



1-20 cells. 

 1-2 cells. 



1-2 ceUs. 

 1-2 cells. 



1-2 cells. 



Solution. Normal S. W. 



4hrs. 

 4 hrs. 



4 hrs. 

 15J hrs. 

 15J hrs. 



15£ hrs. 



15* hrs. 



lhr. 



lhr. 



lhr. 



lhr. 

 16 hrs. 



16 hrs. 

 16 hrs. 



16 hrs. 



Ohrs. 

 Ohrs. 



Ohrs. 



Ohrs. 

 Ohrs. 



Ohrs. 



Ohrs. 

 Ohrs. 



17 hrs. 



17 hrs. 



17 hrs. 



17 hrs. 

 8 hrs. 



8 hrs. 

 8 hrs. 



8 hrs. 



A spindle forms in connection with each germ nucleus, 

 if the poles lie close together triasters or tetrasters 

 form; no vesicular nuclei. Figs. 159-170, 210. 



Chromatin clumped in center of nuclear vesicle; achro- 

 matin fills nuclear vesicle and in mitosis fills amphi- 

 aster; spindles shrunken and no fibers visible; 

 chromosomes scattered; cytasters, but no multipolar 

 spindles. Figs. 183, 189, 190. 



Chromatin clumped in nuclear vesicle; nuclei and 

 spindles shrunken; cytasters, but no multipolar 

 spindles; connective fibers form spindle, widest in 

 middle; achromatin as in preceding, divides ami- 

 totically; no plasma division. 



Chromatin not clumped, but forms a heavy reticu- 

 lum, or spireme; nuclei a little shrunken; cleavage 



2-20 cells; yolk cleavage largely suppressed; nuclei 

 densely chromatic, not vesicular; polyasters, karyo- 

 meres. Figs. 195, 196. 



Chromatin in dense masses; achromatin in numerous 

 separate vesicles, widely scattered, formed from 

 substance of spindles and rays; no spindles; no 

 cleavage. Figs. 184-188. 



Chromosomes do not form vesicles, but achromatin of 

 spindle and asters does as in Figs. 79-82; no cleavage. 

 Figs. 178-182. 



No cleavage; chromatin and achromatin separate and 

 distinct; chromosomes scattered; spindle of homo- 

 geneous achromatin, no fibers; no radiations. 



8-20 cells; blastomeres abnormal in size and position; 

 in resting stage chromatin like spireme; sphere has 

 very definite outline, centrosomes dark and dense in 

 sphere; mitoses few but distinct; chromosomes do not 

 form vesicles, but achromatin and membrane form 

 around them. 



8-25 cells, mostly normal; abnormal only when mitosis 

 has been disturbed; no polyasters, some karyo- 

 meres; scattered chromosomes; chromatic connections 

 between daughter nuclei in few cases. Fig. 221. 



8-25 cells; cleavage normal, development stopped 

 only temporarily; mitoses normal; no polyasters. 



Similar to preceding. 



25-40 cells; cleavage very irregular; yolk cleavage may 

 be suppressed or increased; polyasters and karyo- 

 meres. 



1-8 cells; little cleavage and very irregular; polyasters 

 and karyomeres. Figs. 174, 175, 177, 217. 



1-2 cells; no cleavage, no asters, no centrosomes or 

 spheres; nuclei may be enormous and chromatic, or 

 small and clear; the latter, which were in mitosis at 

 beginning of exp., have not taken in achromatin, 

 which is scattered as homogeneously colored spher- 

 ules. Figs. 171-173, 176, 191, 192. _ 



1-2 cells; similar to preceding; resting nuclei con- 

 stricted and lobulated as in amitosis; big nucleoli; 

 astral rays contracted, spindle fibers fused, chromo- 

 somes scattered; achromatic spherules widely scat- 

 tered. 



