418 



TUNICATA. 



embryonic sac, in consequence of the shortening of the oviduct, shifts towards 

 the epithelial prominence, serves for attaching the sac to the epithelium. 



The development of the female genital apparatus of Salpa (Pegea) bicau- 

 data is quite exceptional. Here (Fig. 208) at about the middle of the body 

 of the individual of the chain, at the right side, there is an outgrowth of the 

 body-wall with a somewhat curved end (genital tube, g, SALENSKY, No. 104). 



FIG. 209. Two stages in the development of Salpa bicaudata (after SALENSKY). In 

 A (a combined figure after SALENSKY), the embryo e still lies at the base of the 

 genital tube (g) within the dilated oviduct. In B, the embryo, at a more advanced 

 stage, has passed out of the tube together with the placenta. , wall of the respira- 

 tory cavity ; b, blood-forming bud (remains of the follicle) ; c, umbilical cord 

 (connection between the embryo and the placenta) ; e, embryo in the dilated oviduct ; 



. el, elaeoblast ; en, endostyle ; f, genital fold ; /?, ciliated pit ; g, genital tube ; i, 

 branchial aperture ; k, gill ; m, aperture of the genital tube ; mt, mantle ; n, nerve- 

 centre ; p, placenta ; pc, pericardium ; st, stolon. 



The lumen of this tube communicates with the atrial cavity (Fig. 209 A). 

 The short oviduct opens far back in the base of this tube between two epithelial 

 folds projecting into the lumen of the genital tube (incubatory folds, /). In 

 spite of this peculiar arrangement, which must be regarded as a modification 

 of the part of the atrial wall surrounding the aperture of the oviduct, it seems 



