37 



We drew water iu our specimen bottles from various 

 parts of the canal, all of which contained the confervas. 

 In about an ounce of the water, otherwise beautifully- 

 clear, I counted 150 separate plants. This would give 

 19,200 specimens of these confervse to each gallon of the 

 water contained in many miles of this canal. 



One of the principal points to which Professor Allman 

 guided our steps was a bridge, under which the Frederi- 

 cella Sultana of Blumenbach and others, was very abun- 

 dant in the crevices of the masonry, about eighteen 

 inches below the surface. These crevices were beautifully 

 fringed with the aquatic moss Fontinalis antipyretica 

 (Linn), and patches of the emerald-green Spongillia, 

 amongst which the brown, unattractive moss-like bunches 

 of Fredericella were very abundant. This curious and 

 beautiful animal, now placed in close alliance with the 

 mollusca, consists of a ramifying brown tubular ccenoecium, 

 of a nature similar to that which contains the polyps in 

 Sertularia and other genera. It consists, however, of 

 two distinct membranes, the inner termed the endocyst, 

 the outer the extocyst. From the orifices terminating 

 the branches of these double tubes the beautiful polypide 

 is protruded or retracted at pleasure, and when expanded 

 is distinctly perceptible to the naked eye. 



The remainder of the morning was consumed in an 

 i;nsuccessful search for the beautiful Cristatella, which 

 the same locality had previously yielded plentifully to 

 Dr. Allman's researches. Near the bridge from which we 

 commenced our explorations, we saw what, if not interest- 

 ing in a natural history point of view, certainly offered 

 food for reflection; a large pile of tan or exhausted 

 tanner's bark, protected from the weather by a temporary 

 covering, formed of some of the beautiful semicircular 

 girders of the roof of the Dublin Exhibition Palace — that 

 splendid roof which formerly spread its ample span over 



