Distribution of Saccaimnina sphserica, etc. 5 



as we know are in some genera (Storthosphsera etc.) the only 

 means of communication between tlie interior and the exteri(jr of 

 the test. Or perhaps he had in view certain larger apertures or 

 " chinks " such as those formed by the angularity of the sand- 

 grains. Such chinks are the normal aperture in the young stages 

 of Saccammina sphmrica before the formation of the nipple-sliaped 

 protuberance which bears the aperture in the adult shell of that 

 species. This matter remains open to doubt. Unless Brady was 

 referring to the porous cement between the sand-grains it appears 

 evident from an extensive examination of specimens of Psammos- 

 pheera fusca from a large number of localities, that he must liave 

 been dealing with either (a) worn or imperfect specimens, or (h) 

 immature specimens of Saccammina sphserica in which, as we have 

 just pointed out, such a " chink " aperture is to be found. 



A careful examination of the numerous specimens of Psammo- 

 sphsera fusca mounted by the late H. B. Brady and preserved in the 

 British Aluseum at South Kensington and in Brady's own collec- 

 tion now, as above mentioned, at Cambridge,* throws no light on 

 the meaninoj of his reference to the " interstitial orifices." There 

 are no specimens exhibiting such openings. But many of the speci- 

 mens are of the neat spherical type since separated by Flint under 

 the varietal name parva, and are built up of minute angular grains 

 of clear quartz. These grains being set at various angles reflect 

 the incident pencils of light in different directions, while in some 

 €ases the ray of light striking a quartz-grain at right angles to the 

 fractured surface passes through into the interior of the sphere and 

 is absorbed. Such particular grains being colourless are practically 

 invisible and look like black gaps in the wall of the sphere. This 

 optical delusion may be the origin of Brady's misleading definition. 

 A similar effect on a large scale may be observed when looking at a 

 lattice-window from which light is reflected towards the observer. 

 Most of the panes of glass are visible owing to the reflection ot 

 light from their surface. Others look like empty dark spaces in the 

 frame owing to the passage of the light-rays unimpeded and unde- 

 flected through the glass. 



In 1894 Dr. L. Ehumbler published a long and exhaustive 



* There are six slides of Psammosphs&ra fusca and four of Saccammina sphserica 

 at Cambridge. Among the former is a complimentary slide from F. E. Schiilze 

 containing two large specimens in fluid, which are probably Saccam,m,ina ; another 

 slide labelled " Challenger 286, S. Pacific, 2335 fathoms " contains rough deep orange 

 spherules which are probably not Foraminifera at all, but concretions, or infiltrated 

 Radiolarians. One slide, " Porcupine 16, W. of Ireland," is P. fusca of the large 

 roughly built spherical type. Two slides, " Knight Errant No. 7, Warm Faroe 

 Channel, 530 fathoms," and " Challenger 122, S.E. off Pernambuco, 350 fathoms," 

 are P. fusca var. parva, some spiculiferous and others not. The last contains 

 " Challenger 122, specimens laid open " (Brady, 5, pi. 18, fig. 7). 



Of the four slides of Saccatnmina two contain typical specimens and are labelled 

 " Knight Errant 7, Faroe Channel, 530 fathoms " and " Porcupine 5, W. of Ireland, 

 364 fathoms." The other two slides contain wild growing and imperfect specimens 

 of Reophax scorpiurus and Hormosina, and one P. fusca, var. parva. 



