4 Tun . 
VI. TUNICATA. 
ciliated ridges of the two sides approximated dorsally and became the 
medullary folds. The ad-oral ciliated band became the peripharyngeal 
bands and the lateral ciliated bands of the endostyle in Tunicata. 
Seeliger (2) in his new “ Bronn” continues the history of the Tuni- 
cata , and brings the account from the beginning of this century down to 
the present time. This is followed by a bibliography (not complete) of 
the group, and then the Appendiculariidce are taken up for detailed treat- 
ment. In the present instalment we have merely the general structure 
of the Appendieularian body, and an account of the remarkable “ Hams” 
or test. It is illustrated by 4 plates, and some cuts giving new figures of 
Appendieularian structure. 
Willey, in his book on Amphioxus and the ancestry of the Vertebrata , 
gives a general account of the structure of the Tunicata , and institutes 
a comparison between Amphioxus and an Ascidian both adult and larval. 
He discusses the development of the Ascidian, the formation of the 
myelonic eye, which he considers as the homologue of the pineal eye of 
Vertebrata , the pneoral lobe, the fixation of the larva, the metamorphosis, 
the change of axis, the formation of additional stigmata, and other 
adult characteristics. He inclines to the view that Appendicular ia is not 
primitive, but has been secondarily adapted to a pelagic life. He later 
on compares the Ascidian larva and Amphioxus larvae with Balanoglossus. 
He concludes that “the proximate ancestor of the Vertebrates was a free- 
swimming animal, intermediate in organisation between an Ascidian 
tadpole and Amphioxus , possessing the dorsal mouth, hypophysis, and 
restricted notochord of the former, and the myotomes, coelomic epithelium, 
and straight alimentary canal of the latter. The ultimate or primordial 
ancestor of the Vertebrates would, on the contrary, be a worm-like 
animal whose organisation was approximately on a level with that of 
the bilateral ancestors of the Echinoderms. , ’ 
B.— ANATOMY, &c. 
Seeliger discusses the supposed segmentation of the tail in the 
Appendicular iidee ( Fritillaria furcata and Oikopleura cophocerca). He 
says that each of the muscle-segments is really a large muscle cell, and 
that parallel lamellae of fibrils extend along the inner side of the cells 
continuously the whole length of the tail. The ganglia in the tail do 
not correspond with the supposed segmentation. 
Lefevre has, also, investigated the tail of some species of Oikopleura 
from the Gulf Stream. He considers that any interruption in the tail 
muscles is artificial, and does not represent a true metamerism. At most 
there is a tendency of the muscle fibres to break at definite intervals, 
which may be, perhaps, the first step towards vertebration. 
Rankin also treats of the same subject, and agrees with the previous 
investigators in regarding the “ segmentation ” as tho result of artificial 
fractures. 
