88 
SHELL GALLERY. 
fixes itself by papillae on the anterior end (Figs. 6, 7). Presently 
the tail becomes absorbed, and the posterior end of the nerve-tube, 
Fig. 6. 
Degeneration of Ascidian Tadpole to form the adult. The black pieces represent 
the rock or stone to which the Tadpole has fixed its head. 
Fig. 7. 
MOUTH 
TAIL 
Very young Ascidian with only two gill-slits. 
(Figs. 6, 7, from Lankester's ' Degeneration.') 
and the brain with its eye and hearing organ, undergo atrophy, the 
nerve-ganglion of the adult alone representing the cerebrospinal 
axis of the larva. The branchial sac and intestines develop greatly, 
