NUCLEOLI IN EUSCH1STUS VARIOLARIUS. 219 



clearly seen in the germinal vesicles of Photos 18 and 19, Plate 

 I., and in the germinal vesicles of Photos 20 to 25, Plate II., 

 and in Photos 26 to 30, Plate III. All these preparations show, 

 that as a rule its position is peripheral and this is also true 

 of the principal nucleolus of the germinal vesicles of Allolobo- 

 pJiora (Photo 31). The absence of a chromatin nucleolus is 

 conspicuous not only in the germinal vesicles of Euschistus but in 

 the young oocytes as well. Compare the young oocytes of Photos 

 1 1 and 12 with the young spermatocytes of Photos I to 5. 



In none of the oocytes, from the earliest to the latest stages 

 do we find a chromatin nucleolus, and its absence in the ger- 

 minal vesicles of Euschistus is made more conspicuous by the 

 fact that a chromatin nucleolus is invariably present in the ger- 

 minal vesicles of AllolobopJiora. If we could find such a struc- 

 ture in the germinal vesicles of Euscliistus, in addition to the 

 achromatic nucleolus, the advocates of the sex determination 

 hypothesis could justly claim it as convincing evidence in support 

 of their theory of its female origin, even if a demonstration of its 

 relation to one of the chromosomes was lacking. 



The absence of a chromatic nucleolus in these germinal vesi- 

 cles cannot be due to the technique since in this case the more 

 delicate achromatic nucleolus would show some disturbance. 

 This point is exemplified in the germinal vesicle of Allolobophora 

 (Photo 31), for in this preparation the pricking has disturbed the 

 large, less chromatic nucleolus, while the small, denser, chro- 

 matic nucleolus remains perfectly intact, and this condition holds 

 true for the hundreds of germinal vesicles of Allolobophora we 

 have preserved. 



It therefore seems fair to assume that the technique is not 

 responsible for the absence of a chromatin nucleolus in the ger- 

 minal vesicles of EnscJiistus. 



In an earlier paper : we ventured to call attention to the like- 

 ness of the chromatin nucleolus in the egg of AllolobopJiora to 

 the chromatin nucleolus of the first spermatocytes of insects. 

 Compare the chromatin nucleolus in EnscJiistns, Photos i to 10, 

 with the chromatin nucleolus in the egg of AllolobopJiora, Photos 

 3 i and 32. In both these forms the chromatin nucleolus stains as 



'Foot and Strobell ('05). 



