454 MOUSE EMBRYO 



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"Standard N omenclature for Inbred Strains of Mice . " 1952, Cancer Research - by Committee on Standardized Nomenclature for 

 Inbred Strains of Mice. 



THE MOUSE EMBRYO: 0.5 TO 2.5 DAYS POST-CONCEPTION 



Fig. 1 - Female mouse at 9 A.M. after previous night of 



mating opportunity showing presence of vaginal plug, 

 certain indication of mating. 



Fig. 2 - Contents of bicornuate uterus after copulation show- 

 ing abudant viscous coagulum containing abundant 

 spermatozoa. 



Fig. 3 - Sperm entrance into the egg cortex, showing disso- 

 lution of the cortex at point of invasion. Note pro- 

 truding sperm tail. 



Fig. 4 - Contents of sperm head, without tail, being reorgan- 

 ized within the egg cytoplasm. 



Fig. 5 - Early stage in polar body formation. Note chromo- 

 somes. 



Fig. 6 - Polar body now separate from egg c>T;oplasm, with 

 distinct nucleus and small amount of cytoplasm. 



Fig. 7 - Extruded polar body quite distinct from the egg. 



Fig. 8 - Large post-maturational female germinal vesicle 

 (nucleus). 



Fig. 9 - Same as fig. 8 but stained heavily to show cell mem- 

 brane and rather granular cytoplasm. 



Fig. 10 - Two pronuclei as they are approaching each other, 



female (larger) on the left and male (smaller) on the 



right. 

 Fig. 11 - Approximation of the two pronuclei, female the 



larger. 

 Fig. 12 - Upper oviduct 0. 5 day after conception showing four 



eggs close together. 

 Fig. 13- Fertilization complete in that polar body is extruded 



and the two pronuclei are approaching each other. 



Male pronucleus appears to swell slightly. 

 Fig. 14 - Both polar boc!' .--r show, but pronuclei are unstained. 

 Fig. 15 - Two cell stage lit 1. 5 days after conception, also 



showing polar body. 

 Fig. 16 - Upper oviduct containing three embr^'os as seen also 



in 

 Fig. 17 - Enlarged view showing two two-cell stages, and a 



single cell with prominent polar body. 

 Fig. 18- Four cell stage. 

 Fig. 19 - Four plus cells, showing persistent polar body, at 



2. S days. 



