sqmnTs, 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 

 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 



BOLTENIA. 



