420 
I.ANCELET. 
to be without gilis, although there is a structure in the gullet 
which answers the same purpose; and Professor Huxley says 
that it does not possess a proper heart; but it has several 
contractile dilations for circulating the vital fluid. 
Such is our account of the Lancelet as it is usually seen; 
but there has been a variation of structure in some one or 
two examples met with, which impresses the persuasion that 
they are of a separate species, although of the same genus; 
for where in the species already described the vent is at the 
hindmost third part of the length, in the instances referred 
to this aperture is about the anterior third part of the body. I 
build less on the fact that the head in this supposed species 
is far more sharp and slender, since this may have been the 
result of accidental injury to the specimen; but the dorsal 
fin begins further back, is less expanded posteriorly, as is also 
the anal, and where they unite to form the tail the membrane 
is short and blunt, and not extended to a point, as in the 
kindred fish. As the vent is far forward the lengthened 
abdominal fin is so much the more so, and it is carried on 
to near the mouth; and, unlike what 1 have ever seen in 
this fin in the former fish, in this instance it has rays, Avhich 
however extend to only half the breadth of the fin itself, 
the border being formed of membrane only; and the anal is 
without visible rays. From the vent to near the tail, along 
the base of the anal fin, is a row of separate points. The 
example here particularly described was received from Glasgow 
by the kindness of David Robertson, Esq., who remarks that 
it was retentive of life; and the question arises whether this 
is the Branchiosioma luhricum of Dr. John E. Gray’s “List of 
Specimens of Fish in the British Museum,” p. 150, a 
native of the Mediterranean. 
Ao^a ©fcco ev xj^iaroit. 
