ANIMALS OF THE WHARF PILES 



89 



a projecting pair of tubes or "siphons," though apparently insignificant, 

 are in reality highly interesting from an evolutionary standpoint. One 

 species (Molgula manhatten- 

 sis) is represented as grow- 

 ing in large yellow masses 

 on the upper part of one of 

 the piles. Some of the in- 

 dividuals of this species are 

 marked with dark starlike 

 colonies of another ascidian 

 (Botryllus gouldii), which 

 grow upon their surfaces. 

 Here and there stand out 

 the conspicuous masses of 

 the pink "sea-pork" (Ama- 

 roucium pellucidum) a colo- 

 nial ascidian whose minute 

 individuals are perceptible 

 as white dots forming irreg- 

 ular ringlike patterns on the 

 colonial mass. On one pile 

 a spreading white patch 

 marks the position of a col- 

 ony of the species Leptocli- 

 num albidum, and here and 

 there bits of delicate web- 

 like net-work dotted with 

 tiny green globules grow 

 over mussels and sea-weed 

 indicating the presence of 

 the green ascidian (Pcro- 

 phora viridis). Some of the 

 ascidians are more or less 

 solitary like the brownish 

 Cynthia partita, and still 

 others (Ciona tenclla) grow 

 in clumps of several individ- 

 uals, comparatively large in 

 size. These have trans- 

 lucent yellowish bodies 

 through which may be seen 



glimpses of the internal organs. The ascidians as a group possess a pecu- 

 liar interest for biologists, since in spite of their humble appearance and 



A typical ascidian, or sea-squirt {Ciona tenella). A 

 food-bearing stream of sea-water enters and leaves the 

 creature's sac-like translucent body by means of the two 

 tubes or siphons 



Large yellow masses of the sea-squirt Molgula, are 

 often found on the submerged piles not far below the 

 water surface 



