2 1 S JORDA N. [Vol. V 1 1 1 . 



entrance of a varying number of spermatozoa into an a^g merely 

 indicates unessential variations in the intensity and duration 

 of nuclear attraction. 



IV. Cleavage.^ 



It is not difficult to obtain the egg of the newt immediately 

 after the female has deposited it, and the order of appearance 

 of the cleavage planes can then be accurately timed. I have 

 preferred this mode of procedure to artificial fertilization since 

 in this way the reproach of departure from the normal is not 

 incurred. 



The first cleavage plane begins from ten to twelve hours 

 after the Qgg is laid. The furrow is vertical and divides the 

 ^gg into two nearly equivalent halves, but usually falls more 

 or less to one side of the exact mid line (Fig. 24, PI, 

 XVII). The furrow reaches the lower pole forty-five to 

 sixty minutes after it first becomes visible at the top of the 



ecrcr 



The second furrow is likewise vertical, and usually cuts the 

 first at right angles near the mid-line, thus dividing the ^g% into 

 four equivalent portions (Fig. 25). The second furrow appears 

 from one and a half to two hours after the beginning of the 

 first, and cuts its way to the lower pole with the same rapidity 

 as the first. 



With the completion of the second furrow all consistent 

 regularity is at an end. The third furrow is often horizontal, 

 but is very variable in position and is usually differently dis- 

 posed in each of the four quadrants. Frequently it can be 

 designated as equatorial only by courtesy, and occasionally it is 

 distinctly vertical. This latter important fact I hope to bring 

 out more clearly presently. 



The point that I wish to touch on first is the great irregu- 

 larity in the early cleavage stages. I have made a careful 

 study of a large number of preserved eggs, and have depicted 

 some of these in Figs. 26 to 32, PI. XVII. These figures con- 



1 1 should here state that I reserve a more detailed consideration of the facts 

 and significance of cleavage for a joint paper soon to appear by Mr. A. C. 

 Eycleshymer and myself. 



