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"Cell division." 12 February 2005. HowStuffWorks.com. <http://health.howstuffworks.com/adam-200110.htm> 12 May 2008.
Cell division
30 hours after conception, the fertilized cell divides into two cells. 15 hours later it divides from two to four cells. After three days there are 16 cells in a structure called a morula. After eight or nine days the structure is called a blastocyst and implants in the uterus.
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"Cell division." 12 February 2005. HowStuffWorks.com. <http://health.howstuffworks.com/adam-200110.htm> 12 May 2008.
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