480 



TUNICATA. 



youngest buds are found to occupy the dorsal middle line, while the older 

 buds shift to the sides of the stolon (Fig. 247). 



Three different forms have been found in the colonies known of Anchinia, 

 but these are regarded by Baerois (No. 77) as fragments of the same stolon in 

 different stages of development. 



I. There are fragments with zooids which, even when developed, remain 

 comparatively small, which are without genital organs and are incapable of 

 reproducing themselves by budding. These zooids are distinguished from 



those of the sexual generation (III.) 

 by the absence of the three pigment- 

 spots and of the papilla-like pro- 

 cesses above the apertures of the 

 body. An accumulation of pigment 

 is found, on the other hand, at the 

 base of the peduncle (Fig. 248 A, 

 "</). On the dorsal side of the tube 

 which bears these zooids a slightly 

 coiled thread is found running longi- 

 tudinally (Fig. 249, st) ; this consists 

 apparently of ectoderm and ento- 

 derm (Fig. 249 B), and is assumed 

 by Barrois to be the actual pro- 

 liferating stolon, from which the 

 buds of this generation grow out 

 laterally. 



II. Fragments with zooids re- 

 sembling in shape the sexual forms 

 (III.) in which also the rudiments 

 of genital organs appear. These 

 rudiments, however, degenerate 

 later. These zooids, which may 

 be compared to the phorozooids of 

 Doliolum, do not seem to reproduce 

 themselves either sexually or asexu- 

 ally. They do not, however, directly 

 nourish the buds of the sexual 

 generation, for these grow out inde- 

 pendently on the colonial tube. In 

 the tube on which these zooids are 

 found, the structure above described 

 as the proliferating stolon is no 

 longer to be seen ; but there are clusters of very small buds which Barrois 

 holds to be derived from the disintegrated proliferating stolon. 



III. Fragments with sexually mature zooids (Fig. 249 B). Each of these 

 zooids is distinguished by the possession of a papilla-like process (p, p') above 

 the branchial and atrial apertures, that over the latter being specially large. 

 On these processes, there are accumulations of pigment ; a third pigment-spot 

 occupies the middle of the body. These zooids are further distinguished by 

 the great depth of the body and the abbreviation of the endostyle (es). The 



£3 



Fig. 248.— A 

 . I nchinia ; 

 Barrois) 



first asexual generation of 

 B, sexual generation (after 

 d, alimentary canal ; es, 

 endostyle ; /:, gill ; p, papilla above the 

 branchial aperture ; p', papilla above 

 the atrial aperture ; pd, peduncle. 



