Hydractinia, Parkeria, and Stromatopora. 69 



tergestina, under a form so like the vents on several kinds of 

 Sponges, where they are outlets of so many systems of super- 

 ficial radiating, branched, excretory canals (which, albeit in their 

 natural state they are grooves or gutters in the dermal struc- 

 tui-e of the sponge converted into canals by the dermal sarcode 

 and rising more or less into monticular eminences respectively, 

 more or less regularly arranged, become mere gutters, as 

 in Bradya tergestina^ when all the soft or sarcodic parts are 

 abstracted, but, if filled with mineral material, might present in 

 relief the same form as in the Stromatopora to which I have 

 just alluded), that, as stated respecting the near proximity of the 

 Hydrozoa and the Rhizopoda {Amoeha and Hydra) , in regard 

 to the spiral structure of Loftusia we might also add here : — 

 there is a near proximity between the Hydrozoa and the 

 Spongida, whereby the stellates of Stromatopora might have 

 been excretory canal-systems in each instance, although the 

 rest of the structure pertains more to the Hydrozoa. 



When we consider that all animal forms are evolved out of 

 simple, apparently structureless sarcode, whether passing or 

 permanent, it is not more surprising that such sarcode should 

 possess the power of movement than that it should be able to 

 assume a definite and beautiful form by movement, ex. gr. the 

 Spongozooti, which, at one moment is a flagellated infusorium 

 and at another a polymorphic piece of sarcode like an Amoeba, 

 or the test of Foraminifera, which is produced by an animal 

 apparently differing very little from a polymorphic Amoeha, and 

 it is not strange that the Hydrozoa, which are so near the latter 

 in the scale of organization, should evolve similar forms. 



The next object to which Mr. Vicary directed my attention 

 is part of a large specimen of a Stromatopora that is suhinjll- 

 trated on the surface, and presents in a most striking manner 

 the vertical tubes and transverse laminae coated with granular 

 calcspar, very like that of the tissue-fibre of Parker ia. With 

 the advantage of thus knowing the exact position relatively of 

 the tubes and laminae, it was not difficult to grind down a 

 fragment of this vertically to the tubes and to the laminae re- 

 spectively. Thus was obtained a direct view of the ends of the 

 tubes on one side (fig. 20), and a longitudinal section of them on 

 the other (fig. 21, a). In the former the tubes were observed 

 to be intimately connected by direct intertubular communica- 

 tion of a smaller kind (fig. 21, Z>), like that uniting the apertures 

 on the surface of H. Vicaryi, and to be scattered throughout the 

 mass of reticulated tissue-fibre indiscriminately — that is, in the 

 midst of the stellates (which are also present here and there ; 

 for, of course, on every layer they are formed, although 

 covered in by the following one, and thus in horizontal or tan- 



