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integument of the body, as viewed from above, below, or one 

 side, appeared distinctly to be composed of several layers, 

 caused, as Mr. Has well informs me, by the outer covering 

 being of quite different substance and consistency from the 

 rest. A series of six narrow ribbons, finely striated longi- 

 tudinally, and lying apparently in one of the inner layers of 

 the integument, formed an efficient muscular system. About 

 once in five seconds, as far as I recollect, they were slowly 

 contracted and more rapidly expanded, the resulting expul- 

 sion of the water in the interior cavity producing a forward 

 jump of about an inch. The sixth band, or ribbon — that 

 nearest the processes at the posterior end — did not completely 

 encircle the body, but was interrupted for a space of about 

 one-sixth of its length, on the dorsal side of the animal — by 

 that I mean the side which was generally uppermost as the 

 Salpa floated, and is opposite to that from which the posterior 

 processes spring. Tlie fifth and fourth bands touched on the 

 dorsal side ; the fourth, third, and second similarly lay in close 

 juxtaposition on the ventral side. 



The water which is ejected by these muscular bands is ad- 

 mitted by a wide orifice, with projecting thick lips, situated 

 in the middle of the anterior end of the Salpa, and these lips 

 were continually and regularly 'opening and shutting. I was able 

 to make a sketch of the orifice, but did not arrive at an examina- 

 tion of the posterior one, which lay somewhere about the long 

 processes. Just behind the anterior orifice, and making an 

 angle of about 45° with the plane dividing the dorsal and 

 ventral halves of the animal, was a roughly triangular purple 

 vein or thread, having in the centre of the space enclosed a 

 purple dot, with a few fine radiating purple lines. These, 

 according to Mr. Haswell's letter, are the nerve ganglion and 

 eye spot. From the centre of the base of the triangular 

 nerve, and running along the dorsal side of the internal cavity 

 of the Salpa is the endostyle, which is purple in colour, and 

 about y% of an inch in length, or f of the length of the Salpa's 

 body. From the apex of the triangular nerve is a similar 

 purple vessel, running in an irregular curve back to the pos- 

 terior end of the animal. This is the main blood-vessel, and 

 close to its further end lies the heart. The heart struck me 

 as very remarkable, and I spent some time in watching it, 

 and noticed that the membranes in it flapped for a period, then 

 paused, then flapped differently, then paused, then flapped as 

 before. I did not then know that these Tunicates have a 

 heart which first drives the blood forward for a certain number 

 of beats, and then backward for a corresponding number. I 

 further noticed a number of globules in the blood thus driven 

 to and fro. This was all of the interior that I had the oppor- 

 tunity of observing and drawing. 



