72 BERTRAM G. SMITH 



the middle and lower portions of the oviduct the eggs are distrib- 

 uted at fairly equal intervals; here the envelope is well formed, 

 and consists of a capsule about each egg, and a slender connect- 

 ing cord, giving a general resemblance to a string of beads. 



After their descent through the oviduct, the eggs of each side 

 of the body form a single string aggregated in a much twisted and 

 tangled mass in the uterus. Considered as individuals without 

 regard to their sequence in the string, the eggs display a striking 

 regularity in their arrangment in the uterus, being packed in par- 

 allel spiral rows; but this is merely the result of mechanical pressure, 

 as the string pursues a very sinuous and complicated course 

 throughout the mass. 



The egg capsules at the end of the uterus nearest the cloaca, 

 hence those first formed, do not contain eggs; those nearest the 

 oviduct, hence the last formed, are likewise devoid of eggs. These 

 empty egg capsules are in general smaller than those that contain 

 eggs, with a regular gradation in size from those at the extremity 

 of the cord, which are scarcely more than a millimeter in diameter, 

 up to those nearest the egg-containing capsules, where the diam- 

 eter is only slightly less than normal. However small the size, 

 these capsules are always perfectly formed, with a central spherical 

 space; they are never solid. The 'empty' capsules contain a 

 small amount of coelomic fluid in which are distinguishable under 

 the microscope leucocytes, erythrocytes and yolk corpuscles. A 

 cloudy mass of fluid with the same constituents occurs in the upper 

 part of the uterus, outside of the egg envelopes. Similar cap- 

 sules devoid of eggs are the 'wind eggs,' known in various verte- 

 brates: birds, reptiles, sharks, chimaeroids. 



As a result of experimental studies on the nature of the stimulus 

 which causes the shell to be formed about the hen's egg, Pearl 

 ('09) reached the following conclusions: (a) the stimulus which 

 sets the shell-secreting glands of the fowl's oviduct into activity 

 is mechanical rather than chemical in its nature; (b) the for- 

 mation of a shell on the hen's egg is brought about by a strictly 

 local reflex, and is not immediately dependent upon the activity 

 of other portions of the reproductive system (nervous impulse or 

 hormone formation). In this connection it is interesting to note 



