LOWEST VERTEBRATE ANIMALS. 25 
direct offspring of the present apes; neither do they 
infer from these observations on the Ascidian larva that 
vertebrate animals are descended from the Ascidians. 
Their accordance much rather forces us to assume an 
unknown primordial vertebrate family, springing from 
some branch of the heterogeneous 
division of the Annulosa, From 
these diverged.on one side the Tes- 
tacea, who might perhaps be called 
mischanced vertebrata, and on the 
other the true vertebrate animals.” 
The Amphioxus which lives in the 
sand in shallow places on various 
coasts, and is daily caught by thou- 
sands at Messina for example, is five 
or six centimetres in length, and is 
compressed after the manner of a OF’ 
fish, pointed at both ends, and semi- M6 4. Ful-grown Ascidian, 
transparent whilst alive. It possesses no trace of limbs, 
at the posterior end only a pair of minute membranous 
margins, the indication of dorsal and caudal fins, and is 
so simple in its internal structure that it is usually, 
though inaccurately, termed a fish. Its skeleton is 
limited to the noto-chord, and some minute cartilaginous 
tods at the mouth and gills. It has no brain, and, 
except a small ciliated sac, perhaps to be interpreted as 
an olfactory organ, no sensory apparatus ; the heart is 
tubular. And thus between the lancelet and other 
true fishes there exists so wide a difference that the 
possibility remains open that the fishes passed through 
some other course of development than phases like 
that of the Amphioxus. 
12 
