354 EYCLESHYMER. [Vol. X. 



irregularities were observed, no greater, however, than occur 

 in normal cleavage. 



Some of the compressed eggs died before the neural folds 

 were formed. A number, however, produced normal embryos, 

 and the longitudinal axis, when compared with the drawings 

 made of the first and second cleavage furrows, showed in the 

 15 eggs examined variations ranging from 5 degrees to 

 45 degrees. 



As a result of pricking the ^.^g, a. minute quantity of proto- 

 plasm was extruded forming extra-ovates which remained 

 attached to the surface of the egg until the embryos were well 

 developed. In a number of cases eggs in the two-cell stage 

 were pricked on either side of the first furrow. I more fre- 

 quently found the extra-ovates on the same side of the median 

 line of the embryo, but occasionally on opposite sides. 



The extra-ovates when detached exhibit interesting phenom- 

 ena, segmenting for a time synchronously with the egg ; the 

 cells arrange themselves so that lighter and darker hemi- 

 spheres are formed. In short, the extra-ovate is a miniature egg. 

 I have not been able to rear any of them beyond the blastula. 



In 5 other experiments a delicate silk thread was tied 

 around the egg in the first and second cleavage furrows. The 

 results were likewise variable ; in 3 eggs the long axis of the 

 embryo formed right angles with the thread, in 2 oblique 

 angles were formed. 



While these experiments indicate that no constant relation 

 exists between the axes of the embryo and cleavage furrows, 

 they are open to the objection that abnormally compressed 

 eggs may reveal nothing of the normal relations. 



Rotation of ovum. — The continuous rotatory movement of 

 the vertebrate ovum so often observed by the older naturalists; 

 Leeuwenhoek, Cams, Sharpey, Bischoff, and others, is a phe- 

 nomenon as yet unexplained. Sharpey, Rusconi, and Bischoff 

 held this to be due to the presence of cilia, yet Barry, Aubert 

 ('54), and others failed to detect their presence, the latter at- 

 tributing the movement to osmotic action. 



In Amphibia (Triton, Amblystoma, Rana) the rotation of 

 the egg within the membranes is most noticeable during the 



