SALPJ3 AND SALPA-CHAINS. 



147 



life of the parent from which it sprung. It is thus, by giving 

 to the young animal a locomotive power which she denies to 

 the fully grown, that nature, in these and many other of the sta- 

 tionary marine animals, provides for the proper dispersion of the 

 species. Among more perfect animals, the old take care of the 

 young, and provide for them ; here we find the young possess 

 instincts and organs which they lose at an advanced period of 

 their life, when they would be no longer necessary, thus beauti- 

 fully balancing the wants and the means of satisfying them. 



While the sessile Ascidise remind one of the polyps, the 

 transparent Salpse, freely swimming in the ocean, bear a great 

 resemblance to the pellucid jelly-fishes, or Medusae. Each 



A. Salpa runcinata solitary. B. S. runcinata associate^, C. S. zonaria aggregated. 



VD. S. maxima. 



a posterior orifice, b anterior orifice, c abdomen, d branchial lamina, e heart. // pro- 

 longations of the test, by which the animal is adherent to its neighbour. 



resembles a crystalline tube, through which one can distinctly 

 see the internal coloured parts. Sometimes these animals are 

 found solitary, at other times associated in circular or length 

 ened groups, termed garlands, ribands, and chains. The salpa- 

 chains, varying in length from a few inches to many feet, swim 

 through the tranquil water with a regular serpentine move- 

 ment, and are often regarded by sailors as sea-serpents ; but 

 when taken from the water, the individuals of the group are 

 easily detached. Thus, in consequence of accidents, separate 

 members of these chains are often met with in seas abounding 

 with these molluscs ; but other separate salpse are also met with 

 that have never been united to others, and differ considerably 



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