that the hypophyseal tube and the ganglion are formed only 

 in part from a common rudiment, and in this respect to take 

 a middle ground between Kjort, Salensky, and Caullery, on the 

 one hand, who have described a common origin for these struc- 

 tures in the Ascidians studied by them, and Oka and Pizon on 

 the other, who maintain that they arise independently. In 

 deriving the hypophysis and ganglion, hov/ever, from tne mes- 

 oderm, I differ widely from all previous observers with the 

 exception of Seeliger. Concerning the origin of the dorsal 

 tube in the buds of Pero pho ra my results are totally opposed 

 to the conclusion of Pizon, which as stated above, is not 

 based on sufficient evidence, namely, that "le tube dorsal 

 des P erophor es a la meme evolution que le tube dorsal des Bo- 

 tryll ides ", (I.e., page 130). 



A study of the younger stages would have convinced 

 him of his error. 



Perophora viridis, at all events, presents an ex- 

 ception to the general rule laid down by Pizon, that "Chez 

 toutes ces families d'Ascidies composees ( Clavelinidae , Pero- 

 phoridae , Botryllidae , Polycli nidae , Distomidae, Didemnidae, 

 et Diplosomida e ) I'organe vibratile debute par un tube aveu- 

 gle, forme par un diverticule de la vesicule endodermique 

 primitive." (I.e., page 131.) 



THE SEXUAL ORGANS. 



:.!y observations on the development of the sexual 



