84 BRITISH TUNICATA. 



individuals the anterior part of the body of which is 

 but little raised (fig. 132). The little red spots being 

 close together around the branchial, aperture, around 

 the superior margin of the branchial sac, and on the 

 line corresponding with the longitudinal folds of which 

 that sac is furnished interiorly, the two rings with 

 eight diverging lines between them represent fairly 

 well the spokes of a wheel. The line of demarcation 



beween the several individuals of the same svstem is 



/ 



not always very distinct. The common cloacal orifice 

 is immediately surrounded by six to eight individuals 



FIG. 132. Botrylloides rotifera. Part of a colony enlarged. (M. 

 Edwards, pi. vi, f. 1 a.) 



only, but lateral branches spring from it having other 

 individuals on each side arranged with tolerable regu- 

 larity, their atrial extremities being directed inwards 

 towards the common centre of the system. The bran- 

 chial aperture is large, and presents inside a circle of 

 tentacular filaments of which four are always well 

 developed, while the others, variable in number, are 

 always rudimentary. 



It is unnecessary to give M. Edwards' description of 

 the branchial sac, heart, stomach, and other internal 

 organs, but the root-like processes which are formed 

 at the inferior end of the tunic are peculiar. They 

 proceed into a common envelope, ramify, and bear at 



