164 The Leptocardii, or Lancelets 
There are no other fins. The alimentary canal is straight, and 
is differentiated into pharynx and intestine; the liver is a blind 
sac arising from the anterior end of the intestine. A pigment 
spot in the wall of the spinal cord has been interpreted as an 
eye. Above the snout is a supposed olfactory pit which some 
have thought to be connected with the pineal structure. The 
muscular impressions along the sides are very distinct and it 
is chiefly by means of the variation in numbers of these that 
the species can be distinguished. Thus in the common lance- 
let of Europe, Branchiostoma lanceolatum, the muscular bands 
are 35+14+12=61. In the common species of the Eastern 
coasts of America, Branchiostoma caribeum, these are 35 +14 
9=58, while in the California lancelet, Branchiostoma cali- 
forniense, these are 44+16+9=69. 
Habits of Lancelets.—Lancelets are slender translucent worm- 
like creatures, varying from half an inch (Asymmetron lucaya- 
num) to four inches (Branchiostoma californiense) in length. 
They live buried in sand in shallow waters along the coasts of 
warm seas. One species, Amphioxides pelagicus, has been taken 
at the depth of tooo fathoms, but whether at the bottom 
or floating near the surface is not known. The species are very 
tenacious of life and will endure considerable mutilation. Some 
of them are found on almost every coast in semi-tropical and 
tropical regions. . 
Species of Lancelets.—The Mediterranean species ranges north- 
ward to the south of England. Others are found as far north 
as Chesapeake Bay, San Diego, and Misaki in Japan, where is 
found a species called Branchiostoma belchert. The sands at 
the mouth of San Diego Bay are noted as producing the largest 
of the species of lancelets, Branchiostoma californiense. From 
the Bahamas comes the smallest, the type of a distinct genus, 
Asymmetron lucayanum, distinguished among other things by 
a projecting tail. Other supposed genera are Amphioxides 
(pelagicus), dredged in the deep sea off Hawaii and supposed 
to be pelagic, the mouth without cirri; Epigonichthys (cultellus), 
from the East Indies, and Heteropleuron (bassanum), from Bass 
Straits, Australia. These little animals are of great interest 
to anatomists as giving the clue to the primitive structure of 
vertebrates. While possibly these have diverged widely from 
