3o8 ISfaohide Tatsu. 



firmed by the fact *'in glanzender Weise " (p. 45). Besides 

 repeating Wilson's experiment on enucleated fragments obtained 

 by shaking he also made cutting experiments. In both cases he 

 very seldom saw cvtasters; none of them had centers and they 

 faded earlier than the true asters in the control eggs (p. 36). 

 Centrosomes were never observed in the enucleated fragments. 

 His general conclusion is, therefore, exactly* in agreement with 

 the position taken by Boveri in his Zellstudien IV, /. e., there are 

 two kinds of cytasters, one containing the centrosome, the other 

 devoid of a centrosome. The centrosome of the former are sup- 

 posed to arise solely as division products of preexisting ones, 

 and only the latter can be produced de novo in the cytoplasm. 



Wilson ('04) in his rejoinder to Petrunkevitsch's paper points 

 out that the evidence given in that paper does not sustain this 

 conclusion and that the negative result is insufficient to disprove 

 the formation de novo of the centrosome. The results brought 

 forward in the present paper fully sustain this position. 



VI. CONCLUSIONS. 



My experiments consist in cutting singly unfertilized eggs by 

 horizontal section at two different periods and in treating the 

 enucleated fragments thus obtained with a solution of CaCU. 

 By these experiments I think I have established the facts, {a) that 

 at the period of the metaphase of the first maturation mitosis 

 cytasters can arise at any point of the egg,^ but (^) that prior to 

 the fading of the germinal vesicle cytasters never arise, (c/. foot- 

 note on p. 304.) In all the cytasters developed in enucleated 

 fragments there is a central group of dark staining bodies, which 

 I do not hesitate to identify as multiplied centrioles. It is to be 

 regretted that I did not find in any enucleated fragment either a 

 single centriole or one in division. This, however, does not 

 invalidate the general conclusion for the reason that centers of 

 exactly the same nature as those in enucleated fragments are 

 found in the nuclear division figure in whole CaCl, egg. 



^My experiments show that cytasters appear in the vegetative half. It was, however, impossible to 

 test experimentally whether the cytasters develop in the vicinity of the first maturation mitotic figure. 

 Nevertheless it will not be unreasonable to infer that they may so arise there from the fact that the whole 

 CaClo egg has many cytasters near the animal pole as well. 



