PROBLEM OF HIGHER FECUNDITY 137 



in size from the smallest ooycote, visible only with the aid 

 of a magnifying glass, to the mature yolk ready to burst 

 from its sac. It has been found under normal egg-laying 

 conditions that it requires about two weeks for the egg yolk 

 to grow from the size of a pea to a full-sized yolk. The 

 yolk is matured in the ovary. "When matured it detaches 

 itself and falls into the oviduct. 



The rest of the egg is "made" in the oviduct. This is a 

 large coiled tube, whitish in color, extending from a point 

 just below the ovary to the cloaca. The albumin and shell 

 are put on in the oviduct. This is accomplished more 

 rapidly than is the development of the yolk. The perfect 

 egg with its hard shell can be retained in the cloaca a short 

 time, or several hours, before being laid. 



In passing through the oviduct the egg travels about 24 

 inches. It is forced through this passage by contraction of 

 the oviduct. As the yolk passes into and through the ovi- 

 duct it becomes surrounded by albumin, and finally by the 

 shell. The time occupied by the egg passing through the 

 various sections of the oviduct is estimated by Kolliker as 

 follows : In the upper two-thirds of oviduct, where albumin 

 is formed, three hours; in the isthmus where the shell 

 membrane is put on, three hours, and in the uterus for the 

 formation of shell and laying, 12 to 24 hours. 



Recent investigations by Pearl and Curtis would modify 

 the above statement. (Maine Bulletin 206.) It was shown 

 in their investigations that only 40% of the albumin was 

 formed in the albumin portion of the oviduct; 10 to 20% 

 was formed in the isthmus, or that portion where the mem- 

 brane of the shell is made, and 30% to 40% of the total 

 weight of albumin was added to the egg in the uterus, 

 passing through the shell by osmosis. 



