No. 2.] THE DEVELOPMENT OF THE NEWT. 305 



chromosomes during this process, but owing to the extreme 

 difficulty of deHmitation (see e.g. Fig. 15) this may be only 

 apparent. 



Coincident with this abrupt internal change there becomes 

 visible on the upper pole of the ^^g the well-known " light 

 spot" of amphibian ova, the so-called " Cicatricula " of Prevost 

 and Dumas, the " Keimpunkt " of v. Baer and the " Fovea 

 germinativa" of Max Schultze. This area has been figured 

 for the axolotl Qgg by v. Bambeke ('70), and his figures resemble 

 essentially the fovea of the newt. There is (Fig. 3) an outer 

 ring of brown pigment shading off on the outside into the 

 normal pigmentation of the upper pole, and on the inner side 

 sharply defining the limits of the light area. This light area 

 {cl. sp) encloses within itself a small circular spot of still 

 greater whiteness, in the middle of which is a minute dark 

 spot. This superficial marking is usually found on all eggs 

 taken from the body-cavity and oviducts, and persists for about 

 two hours after the Q.g^ is laid. It then slowly disappears and 

 the surface of the &gg resumes its original uniformity. 



The internal changes that give rise to this constant ex- 

 ternal appearance are in the main identical with those that 

 have been described by O. Schultze in Siirdon and other 

 amphibia. The germinal vesicle towards the end of matura- 

 tion slowly presses nearer to the periphery of the Qgg, and 

 before the egg leaves the ovary the position of the vesicle is 

 betrayed by the "light spot" due to contrast of the vesicle 

 with the surrounding Qgg substance. The pigment and yolk 

 are of course pushed to one side by the advancing vesicle. 

 Then steps in the abrupt vesicular dissolution above described. 



Sections through eggs from the body-cavity (Fig. 21) show 

 a well-formed spindle which often exhibits a striking accumu- 

 lation of pigment at the two poles. The spindle itself is 

 undoubtedly the basis of the small white spot seen in the 

 midst of the light area (Fig. 3), while the pigment at the 

 peripheral pole of the spindle causes the minute central point 

 of black. The neighborhood of the spindle is occupied by the 

 debris of the vesicle together with small invading yolk spheres. 

 Except in immediate proximity to the spindle, pigment gran- 



