538 
Reginald Ruggles Gates 
and in the larvae cleavage without growth takes place, he deduced 
the law tliat “The cell-size in sea-urchin. larvae is directly propor- 
tional to tbe number of cbroinosomes”. Tbis being tbe case it fol- 
lows tbat “Witb increase in cbromosome number tbe nuclear volume 
grows faster tban tbe corresponding cell volume”. 
Tbe conspicuous cell walls in plants makes it easy to measure 
tbe size of tbe cells directly, and as already seen, tbe results ob- 
tained in 0. gigas are partly in agreement with Boveri’s law and 
partly at variance witb it, tbe relative cell size being in one tissue 
2 : 1, but oftener 1.5 : 1, and in some tissues 3 : 1 or even nearly 4 : 1. 
Boveri concluded (1. c., p. 59) tbat tbe cbromatin is non-regul- 
able and, in case of decrease, unregenerable, tbe protoplasm on tbe 
contrary olfering tbe füllest regulative activity. Tbis of course places 
the cbromatin in a special position among cell constituents. Tbe 
Kernplasma relation, or tbe proportion between nuclear muss and 
protoplasm mass, was considered to be a constant (p. 68). 
Erdmann (1908) in a recent paper regards the matter in anotber 
light. She studied tbe effect of temperature on cell size in sea-urcbin 
larvae at temperatures respectively of 20° C., 15° C., and 10° C., 
fiuding the relative sizes to be 1 : 1.4 : 2.8. Tbe cbromatin volume 
also varies witb tbe temperature. Although tbere was increase in 
cbromatin, tbe chromosomes were found to diminisb in size from 
cleavage to cleavage, those of tbe pluteus having only about 1 J i0 
tbe volume of tbe cbroinosomes on the cleavage spindle. 
Boveri’s final Statement of bis law (1905 p. 74) is as follows: 
»Die Größe der Larvenzellen ist eine Funktion der in ihnen enthal- 
tenen Cbromatinmenge, und zwar ist das Zellvolumen der Chromo- 
somenzahl direkt proportional.« Erdmann’s measurements confirm 
tbe first part of tbis, but she concludes tbat the mass itself, and not 
tbe number, is tbe factor concerned. But in 0. gigas tbe number 
of chromosomes bas beeil doubled and direct measurements sbow 
tbat tbe larger cells and uuclei result 1 ). 
T , r ^ , xi x x- cbromatin mass 
Erdmann further sbows tbat the ratio , — varies 
nuclear surtace 
witb tbe temperature and tbe stage of development while tbe cbro- 
mosome number remains constant. For instance, in tbe blastula 
v Perhaps it would be more accnrate to say tliat the doubling of the chro- 
raosouies and the increase in cytoplasm occurred simultaneously. 
