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TRANSPARENT ASCIDIA. .241 



of my vivaria^ a pan containing marine plants and 

 animals that have been undisturbed for several weeks, 

 I found, attached to a sea-weed, a tiny globule of 

 jelly, not bigger than one of those little spherules 

 wherewith homoeopathy supplants the jalaps and 

 rhubarbs that our grandmothers believed in, and 

 swallowed. It is an Ascidian mollusk, one of that 

 tribe of humble animals that form the link by which 

 the oyster is connected with the zoophyte ; and it 

 appears to belong to that genus that the learned 

 Savigny has named Clavellina. Transparent as the 

 purest crystal, it needed only to be transferred in a 

 drop of its native sea-water to the stage of the micros- 

 cope, and the whole of its complex interior organism 

 was revealed. The old sage's wish that man had a 

 window in his breast, that we might see into him, was 

 more than realised in this case : the whole surface of 

 the little animal was one entire window ; its body was 

 a crystal palace in miniature. (See Plate XV., fig. 1.) 

 To form a correct notion of this tiny creature, 

 imagine a membranous bag, about as large as a small 

 pin's head, with an opening at the top and another 

 very similar in one side ; the form neither globular 

 nor cubical, but intermediate between these two, and 

 rather flattened on two sides. One of the orifices 

 admits water for respiration and food; the latter 

 passes through a digestive system of some complexity, 

 and is discharged through the side aperture. The 

 digestive organs lie chiefly on one side, the opposite 

 to that which forms the principal subject of my ex- 

 amination : they are but dimly indicated in the accom- 

 panying sketch, and I shall not further notice them. 



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