Chap. VI. 
AFFINITIES AND GENEALOGY. 
205 
Negative characters ; it can hardly be said to possess a 
brain, vertebral column, or heart, &c. ; so that it was 
classed bv the older naturalists amongst the worms. 
Many years ago Prof. Goodsir perceived that the 
lancelet presented some affinities with the Ascidians, 
"hi cl i are invertebrate, hermaphrodite, marine crea- 
tures permanently attached to a support. They hardly 
appear like animals, and consist of a simple, tough, 
leathery sack, with two small projecting orifices. They 
belong to the Molluscoida of Huxley — a lower division 
of the great kingdom of the Mollusca ; but they have 
recently been placed by some naturalists amongst the 
Kermes or worms. Their larvae somewhat resemble 
tadpoles in shape , 21 and have the power of swimming 
freely about. Some observations lately made by M. 
Kovalevsky , 22 since confirmed by Prof. Kuppfer, will 
f°nn a discovery of extraordinary interest, if still further 
extended, as I hear from M. Kowalevsky in Naples he 
bas now effected. The discovery is that the larvae of 
Kscidians arc related to the Yertebrata, in their manner 
°f development, in the relative position of the nervous 
system, and in possessing a structure closely like the 
c horda dorsalis of vertebrate animals. It thus appears, 
b we may rely on embryology, which has always proved 
fhe safest guide in classification, that we have at last 
gained a clue to the source whence the Yertebrata have 
21 I had the satisfaction of seeing, at the Falkland Islauda, in April, 
^33, and therefore some years before any other naturalist, the loco- 
Motive larvre of a compound Ascidian, closely allied to, but apparently 
genetically distinct from, Synoicum. The tail 'was about five times as 
r,tl g as the oblong head, and terminated in a very tine filament. It 
) Vas plainly divided, as sketched by me under a simple microscope, by 
fans verse opaque partitions, which I presume represent the groat cells 
gured by Kowalevsky. At on early stage of development the tail was 
el ° se ly coiled round the head of the larva. 
“ ‘Memoires de l’Acad. des Sciences de St. PeTershourg,’ tom. x. 
No - 15 , 1866 . 
