504 



TUNICATA. 



Originally, therefore, the rudiments of the individuals (buds) are 

 nothing more than the consecutive segments of the stolon marked off 

 one from the other by transverse furrows. These furrows, as seen 

 from above or below, are soon no longer transverse, but run somewhat 

 obliquely (Fig. 274), in alternating directions, so that furrows 1, 3 



and 5 are parallel on the one hand, 



jj JJ ~D and furrows 2, 4 and 6 on the other. 



In this oblique course of the furrows, 

 we see the first preparation for the 

 later biserial arrangement ; it is 

 the expression of the lateral displace- 

 ment of the tissues of the buds 

 forming the different segments of 

 the stolon. When, therefore, in 

 later stages, the segments shift to 

 the two sides, it appears as if the 

 buds arose as lateral outgrowths 

 from the stolon. This erroneous 

 view of the budding of the Salpa is 

 actually adopted by many of the 

 older authors. BROOKS was the first 

 to trace back the origin of the buds 

 to the transverse division of the 

 stolon. 



The individuals become more and 

 more sharply marked off from one 

 another in proportion as they assume 

 th^ir lateral positions and project out 

 from the stolon. They then appear 

 to be hanging on to the remains of 

 the stolon like grapes on a bunch 

 (Fig. 275 B\ The remains of the 

 stolon (st), however, are nothing 

 more than the consecutive strands 

 which connect the individuals. 

 These, as may be seen from the 

 diagram (Fig. 272), originally ran from the haemal side of each 

 individual to the neural side of the next older bud. They are 

 originally inserted at the middle of the body. In later stages, 

 when the individuals have taken up the lateral position and have 

 undergone rotation, the connective strand forms a continuous longi- 



FIG. 273. Diagram of a stolon of 

 Salpa after the lateral shifting of 

 the buds has taken place ; the 

 Salpae in this diagram are all repre- 

 sented in the position of individual 

 5 in Figs. 270 and 271. P, proxi- 

 mal ; D, distal ; R, right ; L, left ; 

 r and I, right and left halves of the 

 buds ; a-a, line separating one indi- 

 vidual from the next ; ec, ectoderm ; 

 en, entoderm. 



