SQUIRTS, POLYPS, AND JELLY-FISHES. 57 
In the tangle of eel-grass which here and there 
shows itself you may have had occasion to notice 
that many of the blades are encased 
in a gelatinous or slimy substance, 
whose surface exhibits beautiful 
stellate impressions or markings. 
The whole encrusting mass is a 
compound tunicate or ascidian, the 
rays of the different stars being the 
_ individuals that make up the colony. 
The sharp eye, or, still better, a 
magnifier, will detect in each ray a 
minute speck, which corresponds to 
the incurrent opening in the com- 
mon sea-squirts, and through which 
the water passes in the ordinary 
fashion. In the centre of the star 
is a second speck, which is the 
common excurrent aperture for the 
different individuals of the group. 
Although much reduced in size, 
this compound tunicate, known as 
Botryllus, is constructed on the BOLTENIA. 
same general plan as the larger 
forms above described. In color it varies con- 
siderably, but generally it is of .a livid green or 
a slimy white. Another interesting form which 
can be sometimes found in the grass occurs in 
more or less globular or flattened jelly-like masses, 
ranging in size from an orange to a big cake, 
and having a color much like that of boiled salt 
pork, whence the name ‘sea-pork. The stellate 
