74 EXPEEIMENT STATION EECORD. [Vol.36 



production of dwarf eggs to other abnormal phenomena of reproduction wliich 

 either occur in nature or liave been exi)erimentally produced; and (10) the 

 contribution which the study of the physiology of dwarf-egg production makes 

 to our knowledge of the normal physiology of egg production. The investiga- 

 tions were made at the Maine Station from February, 1908, to February. 1916, 

 during which time 298 dwarf eggs were known to have been produced at the 

 poultry plant of the station. 



During the two years of maximum dwarf-egg production the ratio of dwarf 

 eggs to normal eggs was 1 : 1,1.58. It was found that there were two distinct 

 types of dwarf eggs in respect to their shape, the prolate-spheroidal type similar 

 to the normal egg and the cylindrical type which is much longer in proportion 

 to the breadth. Only 4.6 per cent of the eggs examined were of the cylindrical 

 type. About two-thirds of the dwarf eggs examined contained yolk, which in 

 the large majority of cases was not inclosed in a yolk membrane. A comparison 

 of the mean egg size of the several groups of dwarf eggs confirmed the evi- 

 dence obtained from a study of normal and multiple-yolked eggs (E. S. R., 31, 

 p. J570) that the amount of yolk (or other nucleus) present in the oviduct is 

 an important factor in determining the amount of albumin secreted in a given 

 case. The correlations between yolk weight and egg weight and between yolk 

 weight and albumin weight in dwarf eggs with small yolks were very high. Of 

 the dwarf eggs collected during this investigation 70.8 per cent were laid dur- 

 ing the five months from March 1 to July 31. The dwarf-egg production was 

 also highest in proportion to the normal-egg production during the spring and 

 early summer. 



It was found tliat the production of a dwarf egg is usually an isolated phe- 

 nomenon ; that is, a bird usually produces only one such egg. The 2.51 dwarf eggs 

 of known origin in these studies were laid by 200 birds. Of these 200 birds 

 178 produced 1 dwarf egg each, 15 produced 2 dwarf eggs each, 3 produced 3 

 dwarf eggs each, and 4 produced 4, 5, 8, and 17 dwarf eggs each, respectively. 

 Most of these birds had a normal egg record, and the dwarf egg was preceded 

 and followed by normal eggs. 



A study of all the egg records and the available autopsy records for birds 

 which produced one or more dwarf eggs showed tliat in most cases the dis- 

 turbance which caused the production of the dwarf eggs was of temporary char- 

 acter and was not correlated with a morphological disturbance of the sex 

 organs. The records of only 11 of the 200 birds showed evidence of a permanent 

 disturbance of the egg-forming processes, and these 11 included all the cases 

 where the bird produced more than three dwarf eggs, two that produced three, 

 one that produced two, and four that produced only one dwarf egg. In these 

 11 cases few or no normal eggs were produced after the dwarf egg or eggs, 

 although nesting records indicate that the ovary passed through normal re- 

 productive cycles. Autopsies were made on five of these cases, and all of them 

 showed some pathological condition of the oviduct which interfered with the 

 passage of the egg, but did not entirely close the duct. Dwarf-egg production 

 was found not to be associated with immaturity. 



Data on the position of the dwarf egg in the clutch and litter show that the 

 dwarf eggs may be produced at any time during the laying period. Of 183 

 dwarf eggs produced by normal birds which completed the period of produc- 

 tion during which the dwarf egg was laid, 8 were first and 11 were last eggs 

 in their re.spective litters. "A dwarf egg may be overtaken by a normal egg and 

 form one of the components of a compound egg similar to a double-yolked egg, 

 except that one part is a dwarf egg. A dwarf egg, after it has received its 

 membrane or its membi;ine and shell, may be returned up the duct and be in- 

 cludetl in the succeeding normal egg, or it may act as the stimulus for the 



