Explain why counting degenerated corpora lutea produces an overestimation of actual litter size?
As I understand the definition, a corpus lutea is the vacant spot occupied previously by an ovum within the ovary, now filled by a yellow body that is clearly not an ovum. Couple with that the term "degenerated", which means whatever was there to replace the spot that once held the egg has now decomposed somewhat, and you have a total misrepresentation of a potential litter offspring. You are literally counting "chickens before they hatch". It would be a foolish move, indeed, to include these masses as viable offspring, because they do not consist of such material. They are spots filled with some type of glandular liquid, but are hardly the genetic material needed for the production of healthy, viable offspring. One would be much more accurate to count only the existing ova available for fertilization to calculate the number of litter.