• •. 



Microns 



40 



Figure 303. — Oil globules in the unfertilized egg of C. 

 virginica after staining in Sudan III. Whole mount. 

 Drawing made from a photomicrograph. 



Microns 



40 



Figure 304. — Unfertilized egg of C. virginica stained with 

 Black Sudan B; slight pressure on a coverslip forces 

 the oil globules through the vitalline membrane. Drawn 

 from life. 



that the development of eggs of the Portuguese 

 oyster, C. angulata, is not affected by tohiidin blue 

 used in such dilute solution for only a short time. 

 The dye is fixed at the level of the small granules, 

 which the cytologists designate as alpha granules, 

 uniformly distributed in the cytoplasm between 

 the yolk vesicles. Later in the development of a 

 fertilized egg, new and larger granules, called beta 

 granules, appear at the time of prophase. Their 

 higher metachromasy is acquired at the expense 

 of the alpha granules. Subsequent studies (Mul- 

 nard, Auclair, and Marsland, 19.59) have suggested 

 that the beta granules are related to the Golgi 

 complexes of the eggs. 



The alpha granules of the unfertilized eggs of C. 

 angulata can be separated from the yolk vesicles by 

 centrifuging; they are displaced in the direction of 

 the centrifugal force (Pasteels and Mulnard, 1957), 

 while the beta granules at the pronucleus stage of 

 the fertilized egg are moved in the centripetal 



EGG, SPERM, FERTILIZATION, AND CLEAVAGE 

 I733-S51 O— &4 22 



direction. The alpha and beta particles of Pasteels 

 and Mulnard probably correspond to the P and L 

 granules of Cleland. Personal observations show 

 that in ripe but unfertihzed eggs of New England 

 C. virginica stained with toluidin blue, elements 

 corresponding to the alpha particles of Pasteels 

 assume a lavender color while mitochondria and 

 other smaller granules are bluish. The nucleolus 

 is also of bluish color. After 10 minutes of centri- 

 fuging at 4,000 times gravity the yolk granules of 

 the stained eggs concentrate at the lower (centri- 

 fugal) pole, while the alpha particles of lavender 

 hue and slight!}^ bluish mitrochondria are at the 

 opposite pole (fig. 306). 



Metachromatic granules have been described in 

 the eggs of various bivalves. They were found 

 in Barnea Candida (Pasteels and Mulnard, 1957) ; 

 Mactra (Kostanecki, 1904, 1908; Mercenaria 

 {Venus) mercenaria, Alytilus edulis, and Spisula 

 solidissima (Worley, 1944; Kelly, 1954, 1956; 



333 



