Dr. T. Williams on the so-called " Water-vascular System." 133 



Parasitic ou the thallus of Thelotrema lepadinum, Ach., and on 

 holly. lugleby Park, Cleveland, Yorkshire ! Mr. W. Mudd. 



Thallus undistinguishable from that of the matrix, or a mere 

 film on the bark of the holly. Apothecia apparently bursting 

 through the bark, either singly or in groups of two or three to- 

 gether, stipitate, about \ of an inch high, of a rich dark-brown 

 colour, more or less polished and shining. Stipes smooth. Ex- 

 cipulum clavato-pyriform, truncate at the summit, and incurved 

 at the round depressed orifice. Disk minute, dark brown. Asci 

 linear. Paraphyses very long and slender. Sporidia eight, very 

 large, elliptical, pointed at the extremities, generally rather 

 broad, sometimes narrower and more elongated, of an umber- 

 colour, 3-septate, the cells filled with round granules. 



The immense sporidia preserve this as quite distinct from any 

 other species of Sphinctrina. 



This lichen we owe to the research of Mr. W. Mudd. 



Plate VIII. fig.20. Sphinctrina septata, Leight,, nat. size. Fig. 21. Apo- 

 thecia, magnified. Fig. 22. Orifice of apotliecium. Fig. 23. 

 Section showing asci, sporidia, and paraphyses. Fig. 24. Spo- 

 ridia, highly magnified. Fig. 25. Scale of magnitude of the 

 sporidia only. 



XI. — On the so-called " Water-vascular System." By Thomas 

 Williams, M.D., F.L.S., Physician to the Swansea Infirmary. 



To the Editors of the Annals and Magazine of Natural History. 



Gentlemen, 

 My recent researches have convinced me that the ideas of 

 naturalists with reference to the so-called "water-vascular sy- 

 stem ^^ in the Annulose and Radiated classes, as most probably 

 in the entire subkingdom of the Invertebrated animals, must 

 undergo a radical change. 



Already, in another place, I have pointed out that the ciliated 

 tubes in the Rotifera, to which this title has been given, have 

 nothing whatever to do with water, unless the cavitary nutritive 

 fluid be called by that name. 



1 . At one time I supposed that the convoluted cords described 

 by Hollard, Fi'cy and Leuckart, in the perivisceral spaces ot 

 Actinia, were in truth a rudimentary "water-vascular system.^^ 

 But I now believe that they have no relation whatever to such a 

 system ; that, on the contrary, they are organs upon which is 

 engrafted the reproductive apparatus, and by which at the 

 same time is fulfilled the function of discharging externally the 

 fluid contained in the perivisceral cavity. 



2. I am convinced from recent observations that the so-called 

 "water-vascular system" (Siebold and others) of the Trematode 



