STRUCTURE AND FUNCTION IN MAMMALIAN EGGS SI 



several particulars from that of blood serum. One day before 

 implantation (Day 6), the fluid contains very little protein or glucose, 

 but the concentration of both substances approaches that in serum 

 by Day 8 ; data showed that the increase was due to passage of the 





Fig. 66 

 Dog blastocysts as seen by dark-ground illumination. 

 (E. C. Amoroso.) 



65. 



substances to the blastocyst from the maternal blood stream. During 

 the same period, the phosphorus content doubled and the chlorides 

 increased about threefold. On the other hand, the concentrations of 

 potassium and bicarbonate were higher on Day 6 than later and 

 declined to maternal serum levels as implantation proceeded. 

 Thiamin, riboflavin, nicotinic acid and vitamin B12 were all present 

 in assayable amounts in the blastocyst fluid (Brambell and Hem- 

 mings, 1949; Jacobsen and Lutwak-Mann, 1956; Kodicek and 

 Lutwak-Mann, 1957; Lutwak-Mann, 1954, 1959, i960). 



Shortly before implantation, the guinea-pig egg displays a num- 

 ber of slender protoplasmic processes which extend out through the 

 zona pellucida from the abembryonal cells of the blastocyst (Spee, 

 1893, 1901; Blandau, 1949a, b; Amoroso, 1959). These processes 

 move about actively, rather in the manner of pseudopodia, and are 

 considered to play an important role in the initiation of implanta- 



