UROCHORDA. 31 



The lateral buds are developed in regular order on the two sides 

 of the stolon, and the most advanced buds are those furthest removed 

 from the base. They give rise to forms with a very different organ- 

 ization to that of the parent. They are compared by Gegenbaur to 

 a spoon, the bowl of which is formed by the branchial sack, and the 

 handle by the stalk attaching the bud to the stolon. The oral open- 

 ing into the branchial sack is directed upwards : an atrial opening is 

 remarkably enough not present. The branchial sack is perforated by 

 numerous openings. It leads into an alimentary tract which opens 

 directly to the exterior by an anus opposite the mouth. 



The stalks attaching the more mature buds to the stolon are 

 provided with ventrally directed scales, which completely hide the 

 stolon in a view from the ventral surface. 



These buds have, even after their detachment, no trace of genera- 

 tive organs, and shew no signs of reproducing themselves by budding. 

 Their eventual fate is unknown. 



The median dorsal buds have no such regular arrangement as the 

 lateral buds, but arise in irregular bunches, those furthest removed 

 from the base of the stolon being however the oldest. These buds 

 are almost exactly similar to the original sexual form ; they do not 

 acquire sexual organs, but are provided with a stolon attached on the 

 ventral side, in the sixth inter-muscular space. 



This stolon is simply the stalk by which each median bud Avas 

 primitively attached to the stolon of the first asexual form. 



From the stolon of the median buds of the second generation 

 buds are developed which grow into the sexual forms. 



The generations of Doliolum may be tabulated in the following 

 way. 



Sexual generation, 



1st asexual form with dorsal stolon, 

 I 



spoon-like forms developed as 2nd asexual forms developed as 



lateral buds (eventual history median buds with ventral stolon, 



unknown). 



Bexnal generation. 



Bibliography. 



(6) P. J. van Beneden. "Eecherches s. I'Embryog^nie, I'Anat. et la Physiol, 

 des Ascidies simples." Mem. Acad. Roy. de Belgique, Tom. xx. 



(7) W.K.Brooks. "On the development of Salpa." Bull, of the Museum of 

 Comp. Anat. at Harvard College, Cambridge, Mass. 



(8) H. Fol. Etudes sur les Appendiculaires du detroit de Messine. Geneve et 

 Bale, 1872. 



(9) Ganin. " Neue Thatsachen a. d. Entwicklungsgeschichte d. Ascidien." Zeit. 

 f. wiss. Zool., Vol. XX. 1870. 



(10) C. Gegenbaur. "Ueber den Entwicklungscyclus von Doliolum nebst Bemer- 

 kungen iiber die Larven dieser Thiere." Zeit. f. wiss. Zool., Bd. vii. 1856. 



(i i) A. Giard. "Etudes critiques des travaux d'embryogenie relatifs ala parente 

 des Yertebres et des Timiciers." Archiv. Zool. expenment.. Vol. i. 1872. 



(12) A. Giard. "Eecherches sur les Synascidies." Archiv. Zool. exper., Yol. i. 

 1872. 



