149 
the water were observed to course past these spaces without enter- 
ing ; which would appear to be inconsistent with the idea of the 
water entering, for the course of the water, and of the particles float- 
ing in it, must necessarily be the same. The next author was Milne 
Edwards, who announced the open passages as a fact, without going 
into any reasoning or proof upon it. He however started with a 
bias ; for he alludes at the outset to Dr Lister having established 
the fact, which, it will be observed, is stating the results of his ob- 
servations much too strongly. M, Coste followed, and took the 
directly opposed view, holding that the branchial spaces were all 
closed by a more or less diaphanous membrane. Van Beneden 
seems to have halted between the two opinions. But Huxley, the 
last and most formidable of them all, takes Edwards 5 idea up in toto , 
and has informed Mr Murray, that he thinks he has seen the cur- 
rents of water passing through the stigmata in at least two Ascidice, 
viz.. Perophora, and Appendicularia. 
Mr Murray’s observations consisted in feeding the Ascidise with 
coloured sea water, in injecting them, and in actual examination of 
their structure. In those fed with indigo, the coloured material was 
never found on the exterior of the sac, but always deposited on its 
inner wall. Injection by the mouth into the sac failed to push the 
injection through its walls except by rupturing them. Mr Murray 
thought that, under a high power of the microscope, a diaphanous 
membrane was to be seen stretching across the branchial stig- 
mata ; but if so, the membrane was so thin as to be scarcely per- 
ceptible. 
According to Mr Murray, the mode in which the water which 
enters at the oral aperture passes to the anal aperture would there- 
fore appear to be still unknown. 
Mr Murray narrated, also, his dissections of the ciliated sac or 
valvular aperture which lies at the top of the dorsal fold, which at 
one time he had been disposed to think (with the elder Carus) might 
furnish a mode of egress, but satisfied himself that it was rather 
a blind sac, or at least a sac terminating in a very small blood- 
vessel. 
In the course of his investigations Mr Murray made the curious 
discovery, that in Phallusia Virginea the chylaqueous fluid is 
strongly acid. He had not found this quality in any other species 
which he had yet examined, but he thought it probable it might be 
VOL. IV. 
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