The Leptocardii, or Lancelets 483 



There are no other fins. The ahmentary 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, Branchiostoina lanccolatiiin, the muscular bands 

 are 35+14 + 12=61. In the common species of the Eastern 

 coasts of America, Brandiiostoma carihcDum, these are 35+14 

 + 9 = 58, while in the California lancelet, Br anchio stoma cali- 

 forniensc, 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 {Br anchio stoma calijornicnse) in length. 

 They live buried in sand in shallow waters along the coasts of 

 warm seas. One species, Amphioxides pelagicns, has been taken 

 at the depth of 1000 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 Brandiiostoma belclieri. The sands at 

 the mouth of San Diego Bay are noted as producing the largest 

 of the species of lancelets, Brandiiostoma calijornicnse. 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 

 {pelagicns), dredged in the deep sea off Hawaii and supposed 

 to be pelagic, the mouth without cirri; Epigonichtliys icnltdliis), 

 from the East Indies, and Heteroplenron {bassaniim), from Bass 

 Straits, Austraha. 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 



