420 



LANCELET. 



to be without gills, 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 Avith, 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 Avhere 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 I have ever seen in 

 this fin in the former fish, in this instance it has rays, which 

 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 Branchiostoma 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 Oeco ev vyjrKTTOiii. 



