TUNICATES AND ASCIDIANS 



475 



GENUS Salpa 



The animals of this genus are transparent, subcylindrical, 

 smooth, gelatinous bodies encircled by bands of white muscular 

 fiber. They strikingly exemplify alternation of generations. 

 They occur in two distinct conditions, one being solitary, the 

 other consisting of animals united in chains. The solitary indi- 



viduals are about an inch long, and 

 processes at the posterior end. 

 mals reproduce by budding, and 

 viduals in small chains, the ani- 

 in two rows. The chains grow 

 foot or more, and contain 

 of salpas. Each of these 

 produces in turn a sin- 

 single Salpa, and this 

 reproduces by bud- 

 alike only in alter- 

 ist Chamisso, who 

 tween the two 

 Salpa mother 



have two long 

 These single ani- 

 form series of indi- 

 mals being arranged 

 to the length of a 

 twenty to thirty pairs 

 connected individuals 

 gle egg, which becomes a 

 again, like its grandmother, 

 ding. Thus the animals are 

 nate generations. The natural- 

 discovered the relationship be- 

 forms, expressed it as follows: a 



is not like its daughter or its mother, 

 but resembles Salpa chain - its sister, its grandmother, and its grand- 

 daughter. The single zooids liberate many colonies during the 

 summer, which grow rapidly, and in the autumn the chains are 

 exceedingly abundant. The Salpa chains swim about with a ser- 

 pentine movement, and are beautiful, delicate objects with their 

 transparent bodies banded with white, tinged with pink, and 

 streaked with blue. 



SIMPLE ASCIDIANS 



These are solitary and usually fixed ; they are never free-swim- 

 ming, and when in colonies each animal has a distinct test. All 

 the larger ascidians, or sea-squirts, belong to this group. 



GENUS Molf/ula 



Body more or less globular, membranous, attached or free ; 

 orifices on very contractile tubes. 



M. manhattensis. Nearly globular when the tubes are contracted ; 

 usually covered with bits of eel-grass, seaweeds, sand, etc. ; surface a 



