STRATIFICATION OF THE EGG GRANULES 127 



allow further packing of the granules at the centrifugal pole. In the 

 living egg this is seen as a clear layer (Plate XIII, Photograph 5; also 

 Fig. 12, No. 7). 



d. Stratification of Other Species 



Diameters of the eggs in micra are given. The layers in square brackets 

 may or may not be present. Data from E. B, Harvey (1933 a, 1938 a, 

 1947, and unpublished) unless otherwise noted. 



Arbacia lixula (79). Stratifies like A. punctulata (E. B. H.; Callan, 1949, 

 with diagram). 



Arbacia punctulata (74). Oil, clear, mitochondria, yolk, pigment. 



Echinarachnius parma (145). Oil, absent in some, [clear], yolk, clear, 

 mitochondria, neutral red-staining granules (or methylene blue). 



Echinocardium cordatum (125). Yolk, clear, mitochondria; apparently no 

 oil (Monne, 1944b). 



Echinometra lucunter (85, 97). Oil, clear, mitochondria, yolk. 



Lytechinus (Toxopneustes) variegatus (103, 112). Oil, (little), yolk, clear, 

 mitochondria, [clear]. 



Mellita quinquiesperforata (150). Oil, clear, mitochondria, yolk. 



Paracentrotus lividus (90). Oil, [clear], yolk, clear, mitochondria, [clear] 

 (E. B. H.; Callan, 1949, with diagram). 



Psammechinus microtuberculatus (102). Oil, [clear], yolk, clear, mitochon- 

 dria (E. B. H.; Callan 1949, with diagram; Lindahl, 1932c). 



Psammechinus miliaris (98, 115). Oil, yolk, clear, mitochondria (Holter 

 and Linderstrom-Lang, 1940; Runnstrom and Kriszat, 1950 a, with 

 figures). 



Sphaerechinus granulans (98). Oil, clear, mitochondria, yolk, [clear]. 

 (E. B. H.; Callan, 1949, with diagram). 



Strongylocentrotus drbbachiensis (160). Oil, [clear], yolk, clear, mitochon- 

 dria. 



Strongylocentrotus franciscanus {120). Oil, [clear], yolk, clear, mitochon- 

 dria, [clear]. 



Strongylocentrotus purpuratus {80) . Oil, [clear], yolk, mitochondria, clear. 



Tripneustes (Hipponoe) esculentus (84). Oil, [clear], yolk, [clear], mito- 

 chondria, clear. 



In all the forms listed above, the nucleus is at the centripetal pole 

 under the oil cap, except that Monne (1944b) shows it near the centri- 

 fugal pole in Echinocardium cordatum. In Temnopleurus sp? Motomura 

 (1935) states that it is at the centrifugal end. 



