Eugene Howard Harper 351 



allow it to remain with the convex surface clown in the watch-glass 

 through the washing and hardening treatment. Lying on a flat surface 

 tends to warp and often crack the disc. It should be trimmed evenl}^ all 

 around to overcome the tendency to curl in one direction. Occasionally 

 the egg membrane will come off easily before or even after fixation. 

 If not, the sharpness of the knife must be depended on to overcome this 

 difficulty. Of course the knife should strike the inner side of the disc 

 in its descent. 



The abundance of the yolk and its obscuration of other structures 

 would seem to make it desirable to use a stain which should mask the 

 yolk as much as possible. In all but the fertilization stages the nuclei 

 are surrounded by areas tolerably free from granules, and this is especi- 

 ally true of the sperm nuclei in their later divisons, which are sur- 

 rounded by very large granule-free areas. For this reason the iron-alum 

 hgematoxylin stain is workable, and possesses besides an advantage in 

 differentiating certain areas in the cytoplasm during its amoeboid changes, 

 which are less conspicuous with a stain which masks the yolk. The dif- 

 ferent degrees of extraction of the stain in the different areas of the 

 cytojilasm is a highly desirable feature. 



Some Observations on the Breeding Habits of the Common 



Pigeon. 



The fact that the pigeon breeds so readily in confinement makes 

 possible a close observation of its breeding habits. As is well known, 

 the special instincts displayed in connection with reproduction are more 

 highly developed in the pigeon than in the common fowl. These com- 

 plex instincts are associated with monogamy, which reaches a type of 

 development in the pigeon which is very high among birds. For 

 example, the feeding of the young with " pigeon milk " may be men- 

 tioned. It is only with the earlier manifestations of the reproductive 

 instincts prior to egg-laying that we are here concerned. 



It might be supposed that in the case of a domesticated bird breeding 

 readily in confinement, such as the pigeon, some approach might be 

 made toward an exact method for determining the time of fertilization 

 of the egg. The time of egg-laying is approximately definite, as all 

 breeders know. The common pigeon ordinarily lays two eggs at a sit- 

 ting, occasionally only one. The first egg is regularly laid late in the 

 afternoon. The second egg will be laid early in the afternoon of the 

 second day following. 



It is evident that the determination of the time of fertilization of the 

 second egg of the pair and the length of time taken in its passage 



