C. ROUSSELET ON PEROPHORA LISTERI. 335 



present in all Ascidians, appears to be very little understood. 

 It can, however, well be seen in Perophora. 



In two individuals I observed a spherical cellular structure 

 with a dark mass in the centre, situated at the anterior end of 

 the endostyle, in the angle formed by two ciliated arcs which 

 surround the oral aperture, and pass, just above the ganglion, 

 over a small cone projecting into the pharyngeal cavity. In the 

 other members of the colony this structure was absent, and I 

 am unable to indicate its nature. An auditory capsule has been 

 described as situated on the ganglion. The animal has no other 

 sense organs, no appendages, and no limbs. It is permanently 

 fixed, and the only movement it is capable of is a slight con- 

 traction of the mantle, and the closing of its two apertures. 

 The branchial sac does not contract, and the cilia of the stigmata 

 are seen to be driven through the slits by every contraction of 

 the mantle, giving the appearance of so man}' minute shutters 

 being closed simultaneously. 



The mouth is guarded inside, and a little below its opening, 

 by a circle of small non-ciliated tentacles, which stretch across 

 the aperture to keep out, no doubt, unbidden guests. With the 

 current of water entering the mouth, small animals, such as 

 infusoria, Cyclops, larval crustaceans, etc., are taken into the 

 branchial chamber, and being unable to escape through the 

 minute slits, they pass down to the corner where the opening of 

 the oesophagus is situated, through which they are soon forced 

 into the stomach. The animal, however, has no hard or horny 

 part there, nor anything resembling teeth for seizing or tearing 

 the food. 



The lower end of the intestine is surrounded by a loose 

 tissue of spherical cells, out of which a fine duct can be 

 seen to emerge, terminating in that part of the intestine 

 which lies immediately behind the stomach. This struc- 

 ture is no doubt hepatic in function, and the duct is the bile 

 duct. 



Nearly all tunicates are hermaphrodite, and the reproduc- 

 tive organs are stated to be situated in a fold of the intestine. 

 I have been unable to find them in Perophora, nor have I seen 

 any indication of embryos or larval forms in the atrial chamber. 

 Perhaps the season of the year is not favourable for their pro- 

 duction. The only mode of reproduction I have witnessed is 



