MOLLUSCA. 209 



heart was towards the front, and the downward back stream, 

 instead of flowing out at the wound, was poured into the 

 hinder end of the ventricle ; but when the current was re- 

 versed part of the blood was driven for a time through the 

 stump of the peduncle into the water : however, it soon 

 staunched, and all the vital actions went on as before the 

 separation, except that at the beginning of every pulsation 

 there was a slight recoil. 



In one case where the circulation did not extend to an- 

 other animal, one channel, and only one, was open in the 

 peduncle, and in this a small current ran to and fro accord- 

 ing to the direction of the impulse given by the heart. 

 Some animals, which had probably been injured, but were 

 still connected with other vigorous ones, seemed to be in 

 course of absorption. One was observed in which the soft 

 parts were so shrunk as to occupy a small part only of the 

 tunic ; the currents of its peduncle extended into this mass, 

 but the heart, or motion of branchiae, was visible. Upon 

 looking at the same the next day, the tunic was empty, the 

 soft matter and circulation reaching only to the end of the 

 peduncle. I also once noticed a flux and reflux of the blood 

 in a creeping stem, where the current did not communicate 

 with any animal. 



In some of the last mentioned particulars this Ascidia 

 bears a resemblance to the Sertulariae, and, like them, 

 it increases by sprouts : the two streams of the stem run 

 through the bud before its organs are developed. No pro- 

 per motion was seen in the particles of its blood, like that 

 of the Sertulariae. 



In a sessile Ascidia, nearly half an inch in length, of 

 which the coat was too rough and opake to allow an inspec- 



