288 JORDAN. [Vol. VIII. 



Entstehung aus clem Keimblaschen constatiren, wie Balbiani 

 dies ftir Geophilus unci Will fur den Frosch angiebt." Stuhl- 

 mann agrees with Hertwig and Schtitz as to the significance of 

 the Dotterkern. " Der Dotterkern stellt eine Concretion von 

 dem besonderem, von dem gewohnlichem Dotter verschiede- 

 nem Nahrungsmaterial dar, das zu irgend einer Zeit vom Ei 

 resorbirt wird." 



The more recent observers of the Dotterkern have for the 

 most part contented themselves with passing notices of its 

 presence and general characteristics, and have not added ma- 

 terially to our knowledge of its relations and significance. 



I have given this brief historical sketch of the observations 

 on the " Dotterkern " as well for the purpose of calling attention 

 to the interesting problems connected with this body, particu- 

 larly in its occurrence in the Myriopod and Arachnid ova, as 

 for emphasizing the entire absence of homology between the 

 structures usually classed as yolk-nuclei. 



In the newt the yolk-nuclei first become distinctly visible 

 about the time of beginning yolk-formation, at which time 

 several of these bodies appear nearly simultaneously in differ- 

 ent parts of the ^g^. I have always found at least two and 

 sometimes as many as nine in eggs of about the stage shown 

 in Fig. 7. The number of yolk-nuclei in eggs of a more 

 advanced development is no greater, and on the whole averages 

 somewhat less than the number in eggs of this particular stage. 

 I have no conclusive evidence of coalescence of these bodies, 

 but am confident that some of them disintegrate. They all 

 disappear completely some time before fertilization of the Qg^, 

 and I have never been able to detect any trace of them in eggs 

 that contained a maturation spindle. 



In eggs of the stage shown in Fig. 7 the yolk-nuclei appear 

 first as small, finely granular bodies, irregularly shaped and 

 with their outlines poorly defined from the surrounding cell- 

 substance (Fig. 11). They stain more deeply than the cyto- 

 plasm, but still very feebly as compared with the developing 

 patches of yolk. At a still earlier stage I have observed an 

 appearance which can be best interpreted as a localized con- 

 densation of cytoplasm and a consequent greater avidity for 



