166 RAYMOND PEARL 



So far as I am aware the counts here given are the first attempt 

 yet made at anything more than the roughest sort of a guess at 

 the number of eggs in a bird's ovary. While these counts do 

 not give the total numbers they do establish minimum values. 

 A given ovary certainly does not carry any less than the number 

 of visible ova. 



A word should be said as to the method of making the counts, 

 and the meaning of the subdivisions of the table. The counts 

 were made in some cases on fresh, and in other cases on pre- 

 served ovaries. There was found to be little difference in the 

 two methods, as regards the ease and accuracy of counting. In 

 making the counts small pieces of ovary were cut off, and teased 

 apart with needles under water and the visible oocytes on the 

 small fragments counted. In delimiting boundaries where a 

 number of small oocytes were closely packed together, a hand lens 

 was used. No oocyte was counted, however, which could not be 

 seen with the unaided eye. In other words the lens was not used 

 to find oocytes which might otherwise be missed, but merely to 

 aid in the dissecting of the material. 



In the oocyte counts given iji the table it will be noted that 

 these are grouped into four categories. The first class includes 

 ruptured follicles from which the ova have been discharged. A 

 ruptured follicle w^hich is large at the moment the ovum leaves it 

 gradually shrinks in size and is more or less completely absorbed. 

 On the ovary of a hen which has laid, however, there will always 

 be found a certain number of these discharged follicles not yet 

 absorbed. When such follicles get very small it is exceedingly 

 difficult to distinguish them from small oocytes (i.e., undischarged 

 follicles). Undoubtedly there are errors in classification in this 

 respect in the counts, but for present purposes this is not a matter 

 of great importance. If the eye were sharp enough it might per- 

 haps be possible to distinguish a ruptured follicle for every egg 

 which has ever been laid, since it is doubtful if the absorption is 

 ever so complete as to leave absolutely no scar. It is of interest 

 to note that in the counts there is a reasonably close relation 

 between the follicle count and the record of eggs laid. 



