OF EXPERIMENTAL WORK I73 



Nuclear Fluid. — Density about 1.04 (Heilbrunn, 1928, p. 85). Nucleus less dense 

 than cytoplasm, goes to centripetal pole on centrifuging. 



Nucleolus. — Density about 1.14 (Heilbrunn, 1928, p. 85). 



Fertilized Egg. — 2-cell and i6-cell. Same density as unfertilized egg (Lyon, 1907). 



Blastula. — Density about 1.060; heavier than sea water, lighter than egg (Lyon, 

 1906b, 1907). 



Pluteus. — Density between 1.055 ^"<i 1.066 (Lyon, 1907). 



Sea Water. Density in different localities 



Woods Hole 



Tortugas 



Pacific Grove 

 Plymouth, Eng. 

 Naples, Italy 



1.024 at 19-5° C. (Lyon, 1907) 



1.02426 at 21.5° C. (Garrey, 191 5) 



1,0238 at 20° C. (E. N. Harvey, 193 1 a) 



1.0246 (McClendon, 1910b) 



1. 0244-1. 0253 (Leitch, 1934a) 



1.0241 at 12.9° C. (Bolin, from records, 1952) 



1.0266 at 11° C. (Lowndes, 1944a) 



1.0278 at 16° C. (E. B. Harvey, 1933a) 



DENSITY OF EGGS OF OTHER SPECIES 



Arbacia lixula Unfertilized egg with jelly 

 without jelly 

 Echirwmetra lucunter Unfertilized egg 

 Echinus esculentus Similar to Ps. miliaris 

 Paracentrotus lividus Unfertilized egg with jelly 



without jelly 

 Psammechinus microtuberculatus With jelly 

 without jelly 

 Psammechinus miliaris Unfertilized egg 

 Fertilized, i hr. 

 Blastula, 14 hr. 

 Blastula, 20 hr. 

 Gastrula, late, 44 hr. 

 Echinopluteus, early, 68 hr. 

 Sphaerechinus granularis Unfertilized egg with jelly 



without jelly 

 Str. pulcherrimus Without fert. mem. 

 With fert. mem. 



.101 

 .096 

 .04 



(E. B. Harvey, 1933 a) 



(Leitch, 1934a) 



(Lowndes, 1944) 



(E. B. Harvey, 1933 a) 



(E. B. Harvey, 1933 a) 



.083 



•079 



.074 



.072 



.0725 (Lowndes, 1944 a) 



.0736 



.0758 



•0793 



•0839 



.09626 



.083 (E. B. Harvey, 1933 a) 



.081 



.0772 (Hiramoto, 1954) 



.056 



DYES 



See Vital Dyes 



ECHINOCHROME 



See Amoebocytes, Chromatophores 



Name. — Given by MacMunn (1883, 1885, 1889) for the coloring matter in peri- 

 visceral fluid, ovaries and shell oi Echinus esculentus (?), E. sphaera, Strongylocentrotus 

 (Paracentrotus) lividus and Amphidotus (Echinocardium) cordatus. Called "arbacin" by 

 Vies and Vellinger (1928) in Arbacia aequituberculata (A. lixula). 



Occurrence. — In test, eggs, and red amoebocytes o( Arbacia punctulata (McClendon, 

 1912a; Cannan, 1927; et al.). In test is probably present as Ca salt or adsorbed on 

 CaCOs; not readily extracted by organic solvents in which echinochrome is soluble. 

 Can be obtained in solution by digesting shells in acid (Ball, personal communica- 



