IDEXTIFICATION OF SPOILS. 295 



The first thing you have to do on the morrow is to 

 " identify" the animals — a long and interesting, though 

 sometimes perplexing process, owing to the exasperating 

 system adopted by naturalists of frequently selecting, 

 as marks, characteristics by no means obvious. For 

 example, when you read the sentence " shell flexible," 

 among the curt indications by which an animal is to be 

 identified, how are you to suspect that the animal in 

 question has no shell visible at all, until you have dis- 

 sected it, and found the thin calcareous plate under- 

 neath the back, coverino; the liver? That one sentence 

 " shell flexible" prevented my identifying a Pleuro- 

 hranchus for at least an hour. 



Nor have I to this day been able to identify the 

 species of a compound Ascidian (which I only know to 

 be an Ascidian from embryological indications), pro- 

 bably known to naturalists, perhaps yet undescribed. 

 It is of a bright orange colour. From a transparent 

 gelatinous basis minute cylindrical tubes rise, each 

 about the twentieth of an inch in height, standing in 

 circular groups. The orifice of each tube has four de- 

 licate processes radiating inwards, like the spokes of a 

 wheel, or like the processes in the siphon of a cockle. 

 This orifice is alternately protruded and retracted, but 

 does not open and shut like that of an Ascidian ; and, 

 moreover, the orifice is single. The heart, or pulsating 

 sac, lies at the bottom of the visceral cavity. Imbedded 

 in the clear gelatinous base are several branching ves- 

 sels giving ofl" pear-shaped processes. These vessels 

 connect the visceral cavities of the whole colony, and 



