Sept. j8, 1916 Dwarf Eggs 1035 



The results show conclusively that in a certain stage of activity the 

 oviduct responds to a mechanical stimulus by the secretion of the egg 

 envelopes. 



The fact that in a bird approaching a period of laying the oviduct 

 enlarges as the yolk enlarges has long been recognized. In a bird which 

 has not laid for two or three months and is not preparing for another pro- 

 duction period the sex organs are in strictly nonfunctional condition. The 

 ovarian eggs are scarcely larger than a pinpoint. The oviduct is a small, 

 almost straight thin- walled tube, weighing from 2 to 3 per cent of its 

 weight when in functional condition. As the ovary approaches laying 

 condition, the oviduct enlarges. When the first group of oocytes start 

 on their final growth period, t the increase in the size of the duct is per- 

 ceptible. By the time the first yolk is mature, the oviduct is also nor- 

 mally in functional condition. That this correlation is entirely due to 

 the ovary is shown by the fact that the removal of the oviduct has no 

 influence on the development or functional activity of the ovary (23, 16). 

 Normally the oviduct is in functional condition only while the ovary is 

 maturing yolks. The correlation is now commonly attributed to the 

 internal secretion of the ovary. Bartelmez (1) working on pigeons states 

 that "interstitial cells of the ovary show much greater signs of activity in 

 functioning ovaries than do those in ovaries of birds that have not laid 

 for a long time." A fact cited by Pearl and Curtis (16) indicates that the 

 connection is not nervous, or at least that it is not conveyed to the oviduct 

 through the nerves. This fact is that after the removal of a large part 

 of the oviduct any part not removed passes through growth and 

 cyclic changes associated with the periods of ovarian yolk production, 

 exactly as though the duct were intact. Observations made in connec- 

 tion with other researches have shown that enlargement of the oviduct 

 is not necessarily connected with yolk formation, although this is the 

 normal relation. The two classes of exceptions that have been noted are: 

 First, certain hermaphrodite fowls have been observed (14) that have ova- 

 ries largely made up of stroma rich in connective tissue and containing no 

 large follicles, and yet these birds had oviducts from one-half to three- 

 fourths the size of a functional duct ; and, second, birds with certain types 

 of ovarian tumors, but without enlarging yolks, have been observed to have 

 nearly functional-sized ducts. 



These facts taken together indicate that the functional condition of the 

 oviduct depends upon some substance formed in the ovary, usually at 

 the time yolks are maturing, but in certain pathological cases at other 

 times also. This substance is probably an internal secretion carried by 

 the blood, since the ovary can cause the enlargement to functional size 

 of a small piece of oviduct the normal nervous connections of which have 

 been destroyed. The fact that dwarf eggs are produced only when the 

 bird is maturing and ovulating yolks and the fact that more than 50 



