THE PYROSOMA. 359 



which the creature sways like a fritillary on its slender stalk. The two orifices by which 

 water is admitted into and ejected from the system are seen, and their remarkable four -cleft 

 openings are well displayed. When very young, the Boltenia is often found affixed to the 

 stem of its parent. 



The Boltenia, several species, is an unfamiliar animal, unless the observer is interested 

 enough to go to the beaches after storms, when it will be found cast ashore, with great 

 quantities of sea-weeds, kelp, etc. It is always an attractive creature, looking more like a 

 rich peach or damson, with its beautiful pink and lemon coloration. 



Many of the Ascidians are very uninviting in appearance. 



The Cynthia pyrieformis is one of the most beautiful of the race. It is called Sea-Peach, 

 from its rich velvety surface and bright pink blush, precisely the aspect of a blood-peach. 



WE now arrive at the Social Ascidians. Our first example of them is the CLAVELLINA. 

 Its blood circulates through channels of communication, passing to and fro through separate 

 tubes. It is a small creature, and extremely transparent, the latter characteristic making it a 

 valuable species to the physiologist, who is enabled to watch its structure, and the methods in 

 which the different organs perform their duties, without needing to dissect it. The Clavellina 

 may be found on the European shores at low water, adherent to rocks, stones, or sea-weed, to 

 which it attaches itself by means of the tiny root-like projections which are developed from 

 ' the outer tunic, something like the little rootlets by which ivy clings to a wall. 



Our second example is the SYNTETHYS, another European species. When full-grown, a 

 group of these creatures forms a largish mass, nearly six inches in diameter, and as many in 

 height, each member of the group being about two inches long. They are rather transparent 

 and of a greenish color, and, when touched, they will contract themselves violently, and 

 vanish into the common mass on which they are seated. These animals are propagated both 

 by eggs and buds, the buds being produced on offshoots of the creeping tube. Sometimes the 

 young one severs its connection with the parent, and fixes upon some fresh locality, there to 

 form the basis of a new colony, but it frequently remains on the same spot, and only serves to 

 increase the general mass. 



OF the Botryllidse, or Compound Ascidians, we may mention the common STAR-SHAPED 

 BOTRYLLUS. The "tests," or equivalents of the shell of these animals, are fused into a 

 common mass in which these individuals are imbedded. In the present genus the animals 

 are arranged in a star-like form, each group consisting of a number of individuals, not less 

 than six, and not more than twenty, in number. Many of these groups, or systems as they 

 are technically called, are found upon the common test. The branchial orifices are simple, and 

 the other orifice is common to all the members of the group, and forms, as it were, the centre 

 of the radiating star. Six European species are known, which may be found on stones and 

 sea- weed at low- water mark. 



A VERY beautiful and curious mollusk, called from its luminous appearance the PYROSOMA, 

 i.e., Fire-body, is an example of the next family. This is one of the compound tunicates, and 

 looks like a gelatinous cylinder, open at one end, and closed at the other, and having its body 

 covered with numerous zoiids grouped in whorls. A large Italian-iron tube, studded with 

 daisies, will give a good idea of its general shape. 



The ejecting orifices of the aggregated animals all open into the hollow interior of the 

 cylinder, and the consequence of this structure is, that by the constant flow of the rejected 

 water, the whole mass is driven slowly and regularly through the waves. When seen at night 

 they look just as if they were made of glowing white-hot iron, and they are at times so 

 numerous as to choke up the nets of the fishermen, and diffuse so strong a light around them 

 that even the fishes are rendered visible when they happen to swim within the sphere of its 

 radiance. There is generally a greenish hue about the light. 



Of the appearance presented by these animals when existing in great numbers, Mr. F. D. 

 Bennett gives the following vivid and valuable account : " When assembled in the sea, and, as 



