252 ANIMALS OF THE SEASHORE 



Thaliacea 



Salpa democratica Forskuli (Salpa) 



Salpa and related genera pass through an alter- 

 nation of generations. One stage is solitary and con- 

 sists of small transparent, ovoid individuals about 

 an inch long, each with two posterior projections. 

 These simple animals reproduce by budding and 

 thus form long chains, the animals always being 

 arranged in two rows. These chains may be a foot 

 or more in length and may be composed of 30 or 40 

 pairs of Salpas. The individuals of the chain pro- 

 duce eggs and from these eggs new solitary Salpas 

 are formed. Thus the cycle, or alternation of genera- 

 tions is completed. The life history reminds us of 

 that of the hydroids. 



Salpa is often very numerous floating on the 

 surface of the sea and may frequently be collected 

 by a tow net or plankton net. Although able to 

 swim with a snake-like motion, Salpa is usually 

 carried by the currents, and thus belongs to the 

 plankton of the sea. 



Widespread distribution; often very abundant 

 in summer off the New Jersey and New England 

 coasts. 



Simple Ascidians 



Molgula manhattensis De Kay (Sea Squirt; Sea 



Grapes) 



Fig. 44 



A globular form with two contractile siphons or 

 tubes; often found growing in clusters in shallow 



