Ovulation in the Domestic Fowl 159 



It may be objected that the follicular aggregates resulting from the oviducal 

 thread and continuing gonadotropin administration are not comparable, 

 the former representing over long periods an essentially normal hierarchy, 

 whereas the latter comes to include a number of ovulable follicles as well as 

 rapidly growing smaller follicles. The differing ovarian complements may 

 simply reflect quantitative differences in stimulation, since Huston and 

 Nalbandov (35) note that in some of their early experiments, in which key 

 chains and other large irritants were employed, the ovary sometimes carried 

 "six or more follicles of ovulatory size". They observed also, in hens carrying 

 only the oviducal thread, "a few sporadic ovulations which were widely 

 spaced", suggesting a relatively moderate stimulation (and moderate estrogen 

 inhibition) under these conditions. On the other hand, most if not all descrip- 

 tions of the ovary following gonadotropin administration have been based on 

 manifestly heavy stimulation. 



If a continuing oviducal irritant may act in the manner suggested, the 

 oviducal egg during its passage to the uterus may likewise stimulate the 

 elaboration and secretion of estrogen. We have considered already a possible 

 role of varying estrogen concentrations in the ovulation cycle, namely, their 

 participation in timing of successive excitations in a manner which may 

 account, in part at least, for lag and termination of the sequence. Possibly 

 the oviducal egg is of greater importance in this respect than is the release 

 of OIH. Perhaps the actions of OIH and the oviducal egg are related in 

 some fashion not presently suspected. Whatever the facts may finally turn 

 out to be, the role suggested here for the oviducal egg seems in accord with 

 experimental evidence concerning the action of estrogen in the hen's ovula- 

 tion cycle, as well as with a plausible interpretation of the effects of the 

 continuing oviducal irritant. 



It is well known that ovulation may occur in hens whose oviducts are 

 incapable of engulfing the ovulated yolk, either as a result of surgical 

 operations on the oviduct (47) or of naturally occurring conditions (36). 

 The timing of successive ovulations in such hens, not presently known, 

 might tell us much concerning the possible participation of the oviduct in 

 the ovulation cycle. By X-ray or other techniques it should be possible to 

 establish this obviously important datum. 



The Hypothesis of Bastian and Zarrow 



These authors (3) based their hypothesis of the ovulation cycle on the 

 postulation of "two separate and independent cycles" which "interact in 

 such a way as to result in the typical ovulatory cycle of the hen", to result, 

 that is, in the appearance of what we have called lag, and the period of 

 lapse. One of their concepts is that there is present an effective ovulatory 

 stimulus (LH or OIH) over an extended period, e.g. 8 hr, each night, including 

 the night preceding the day during which ovulation fails to occur. According 



