56 CLEAVAGE II 



TABLE VII. 



q fi . Volumes in cubic /* of 



Nucleus. Cell. Chromosomes. 



2 cells 10037-0 106250-0 19-17 



4 cells 1605-8 51063-0 10-83 



8 cells 1081-0 26290-0 8-32 



16 cells 837-8 9973-0 7-24 



32 cells 803-6 6023-0 5-46 



64-132 cells 529-7 2685-5 4-51 



Blastula 1 460-5 1343-0 3-59 



Blastula2 332-4 549-7 2-77 



Gastrula 1 117-4 292-5 1-92 



Gastrula2 62-9 180-7 1-00 



Pluteus 28-7 118-0 0-41 



It seems therefore that not only the cell-volume but also the 

 nuclear volume decreases during segmentation, gastrulation, 

 and the development of the larva, and it is obvious that the 

 nucleus does not grow to the original size after each division. 

 As we should expect from Boveri's work, diminution in the 

 volume of the chromosomes is accompanied by decrease in the 

 size of the nucleus ; since, according to Boveri, the size of the 

 nucleus depends on the number of the chromosomes, originally 

 given to it, and the mean size of the paternal and maternal 

 chromosomes is at least nearly the same. 



At higher temperatures (15-16 and 20) the same diminu- 

 tion of the nucleus and its chromosomes is seen : the absolute 

 values for any stage diminish as the temperature rises. At one 

 and the same stage the number of cells is greater, the higher 

 the temperature. The total amount of chromatin present in 

 the embryo at any one stage (blastula or gastrula) is, however, 

 constant at all temperatures. 



From the data the ratios are at once obtained (Table VIII). 



TABLE VIII. 



Ratios of volumes, 



st o- Cell. Cell. Nucleus. 



Chromosome. Nucleus. Chromosome. 



2 cells 348-0 10-5 32-8 



4 cells 294-0 31-8 9-3 



8 cells 187-0 24-3 8-1 



16 cells 86-0 11-9 7-2 



32 cells 68-0 7-4 9-2 



64-132 cells 37-0 5-0 7-3 



Blastula 1 23-0 2-9 8-0 



Blastula 2 12-0 1-6 7-5 



Gastrula 1 9-4 2-5 3-9 



Gastrula 2 11-2 2-9 3-9 



Pluteus 19-0 4-2 4-3 



