Hydractinia, Parkeria, and Strom atopora. 63 



kind help of my friend Mr. Dallas, I have been permitted to 

 examine), whose granulated sm-face, close to the edge of the 

 section, where it can be identified with the spiral lamina to 

 which it belongs, when viewed with the microscope, aided by 

 the addition of a little water covered by a thin glass disk for a 

 temporary varnish, presents the same reticulated structure with 

 (what were) the circular apertures, now filled with transparent 

 calcspar, varying from 1- to 4-1800ths inch in diameter. This, 

 in comparison with the diameter of the apertures of the radial 

 tubes (viz. 14-1800ths inch) on the natural surface of a 

 Parkeria 1^ inch in thickness, seems very small ; but then it 

 should be remembered that towards the centre of the Parkeria 

 this aperture is not more than 6-1800ths inch in diameter, 

 while in Hydractinia calcarea the apertures do not exceed 

 3|-1800ths inch, and in //. echinata the ccenosarcal stoloni- 

 ferous creeping tubulation is only 5-1800ths inch in diameter, 

 &c. So that, after all, these apertures on the surface of 

 Loftusia were not relatively small. 



Comparing the radial tubes in Loftusia with the single one 

 that unites the successively enclosing chambers of the ovoid 

 Foraminifera termed " Ellipsoidina^'' as Mr. Brady has done 

 (p. 748), would lead one to infer that they finally opened on 

 the surface of Loftusia as in Parkeria^ which is just what 

 might be expected, although not actually stated by Mr. Brady. 

 Undoubtedly there is a great resemblance between the spiral 

 growth of Loftusia and that of the Foraminifera generally, 

 especially Alveolina] but here the resemblance ends; while a 

 " spiral growth " is by no means peculiar to the Foraminifera. 

 The general form also of Loftusia is elliptical, as in Alveolina ; 

 but instead of the sigmoid longitudinal lines dividing the sur- 

 face of Alveolina into segments like those of an orange, with 

 transverse parallel lines between them, we have in Lofusia a 

 minutely granulated surface, irregularly bossed, and sprinkled 

 with papilliform eminences about l-50th inch in diameter 

 (fig. 18, a, h). At least this is what may be observed in the 

 large specimen of the Geological Society's Museum. 



And here it should be remembered that, in studying the 

 fossil structure, the white parts or lines represent the substance 

 of the test, and the dark ones the intervals which were 

 occupied by the sarcode ; at the same time, that a white line 

 may be merely the cylindrical wall of a dark interior, as seen 

 in the radial tubes of Parkeria under section. 



That Loftusia was irregularly bossed during growth may 

 also be seen in the section, which in this respect serves to con- 

 firm what, on the surface, might be doubted, from the quantity 

 of matrix left about the specimens, consisting almost entirely 



