ZOOPHYTES. 327 



fine thread of a pellucid white appearance, so firmly ad- 

 herent that if you attempt to remove it with a needle's 

 point, you find that you only tear either the leaf or the 

 thread. The course is generally in a straight line, but 

 does not ordinarily pursue the same direction far, com- 

 monly turning off with an abrupt angle at intervals of 

 about an inch ; and thus meandering in a zig-zag fashion, 

 very irregularly, branching frequently, and uniting with a 

 thread already formed, when the creeping one has to 

 cross it. 



Thus the basal network is formed; but meanwhile, 

 from every angle, and often from intermediate points, a 

 free erect thread has shot up — like the stem of a tiny 

 plant — to the height of an inch, rarely more ; not, however, 

 straight, but with frequent zig-zag angles, whence the 

 name genictdata, or "kneed." At every angle a slender 

 branch is sent forth, pursuing the same direction as that 

 of the joint from the summit of which it issued, and termi- 

 nating in a tiny knob. In the angles of some of these 

 branchlets are seated oblong vesicles, twice or thrice as 

 large as the terminal knobs. And this is pretty well all 

 that we can make out with the naked eye. 



Cutting carefully off with scissors a narrow strip of the 

 leaf, I drop it into the parallel-sided cell of glass half-filled 

 with sea-water, and examine it first with a low power and 

 afterwards with a higher. We now see that the creeping 

 thread is a tube of horny substance, flattened on its under 

 side, and that the erect stems and their branches are similar 

 tubes, whose cavities are in free communication with that 

 of the creeping root. The wall is thin, and perfectly 

 transparent and colourless ; the whiteness of the whole 

 being dependent on a soft medullary core of living jelly, 

 which permeates the whole structure, on which the horny 

 sheath is as it were moulded. 



This medulla is pierced with a canal, through which a 

 fluid circulates, carrying along numerous minute granules 



