No. 2.] THE DEVELOPMENT OF THE NEWT. 32 I 



lines, and this distortion is carried still further by the next set 

 of furrows (Fig. 33F). Fig. 33E portrays the lower pole of 

 the stage shown in 33D and emphasizes the truly vertical 

 character of the two furrows in the right half, which have here 

 advanced so that they strike the center of the lower pole ; the 

 equatorial tendency of the furrows in the other half of the egg is 

 also confirmed. This egg developed into a perfectly normal 

 embryo, with no visible deviation from the normal course of 

 development. 



I may here anticipate the forthcoming paper by Mr. Eycles- 

 hymer and myself so far as to state that we have convincing 

 evidence that the whole third set of cleavage furrows in the 

 amphibian Qg^ may at times be vertical instead of horizontal 

 and yet result in normal development. This fact has obvious 

 and important bearings upon the question as to the " homologies" 

 in amphibian and teleostean cleavage. 



Axis of the Embryo, etc. — The relation of the first cleavage 

 plane to the axis of the embryo is a point of some interest, 

 although in the light of recent cytogenetic studies it cannot be 

 held to be a matter of such vital importance as was at one time 

 supposed. The Qgg of the newt, as I have stated elsewhere, is 

 enclosed at the time of deposition in an oval, thick-walled 

 membrane. The egg thus enveloped has been submitted while 

 in the oviducts to such compression that for several hours after 

 it is laid it is very much elongated in the direction of the long 

 axis of the capsule. The long diameter of the Q.gg at this time 

 is often double the transverse diameter. Before the formation 

 of the first cleavage plane the Q,gg resumes its spherical form. 

 The first cleavage plane invariably passes through the Qgg at 

 right angles to the axis of the capsule and therefore at right 

 angles to the direction in which the ^gg was elongated by com- 

 pression. If the ^gg be left undisturbed in its capsule it 

 adheres to the bottom of the capsule so firmly that it may be 

 turned bottom upwards without rotating. After repeated 

 observation of the living Q.gg, I am convinced that when the 

 Q.gg thus fixed remains undisturbed and under normal conditions, 

 rotation cannot occur. By the direction of the convexity of the 

 crescentic blastopore (Fig. 35) and while the form of the egg is 



