Organic and Inorganic Changes q/Parkeria. 47 



inch, is just below the centre, so that it is somewhat swollen 

 here, while the upper end is conical and free and the lower 

 one obtuse and fractured, indicative of previous fixation at 

 this point to some submarine body. In composition it con- 

 sists of a whitish-yellow, minutely granular substance like 

 " chalk " intermixed with small tracts that are pure white, 

 while the whole is charged with foraminiferal detritus in 

 which the tests are not only fragmentary but very minute, 

 and for the most part globular in form, of different sizes, like 

 OrhuUna and Glohigerina^ together witli numerous grains of 

 glauconite (fig. 1, a). All around the circumference of this 

 whitish cylindrical nucleus the structure of the Parkeria is more 

 or less obscured by the growth outwards of the dark brown my- 

 celium and filamentous structure of Millarella, of which the 

 former (which should be viewed by reflected light) requires a 

 high power to be distinguished in detail, while the latter is 

 easily seen with a much lower one, when it appears as a 

 glistening white thread more or less branched — the glisten- 

 ing white appearance arising from the minute crystalline 

 matter of which it is now composed. This thread or filament 

 is about l-900th of an inch in diameter, tortuous, and more or 

 less branched ; but wliat its state was when fresh I am not 

 prej^ared to say. Such filaments often form part of a Sapro- 

 legnious Alga ; but I could see no appearance of fructification 

 about them. 



The white chalk-like part represents the oldest and the 

 darker (fig. 1, c) stains (like rot to the naked eye) the youngest 

 parts of the Millarella. Nevertheless the clialk-like sub- 

 stance also is pervaded by the reticulated mycelium, which im- 

 parts to it the " whitish-brown " colour before mentioned, but 

 which can only be seen with a high power, when the presence 

 of the minute fragments of the Foraminifera in it indicates its 

 originally plastic nature. 



It must not be inferred that this kind of nucleus always 

 presents the same shape, for I have several specimens of 

 rarheria in which it is present, wherein both in form and 

 size it is quite different. For instance, in one of these 

 (fig. 2, a) it is globular, about half an inch in diameter, sur- 

 rounded by a dark jagged edge, composed of the brown sub- 

 stance or young structure of Millarella^ which, on account of 

 the light colour of the specimen of Parkeria itself, contrasts 

 strongly with it in this respect, so that the definition of the 

 nucleus is very marked, while it is by no means situated in 

 the centre of the Parkeria^ but, on the contrary, towards the 

 circumference, where it communicates with the exterior by a 

 small contracted neck (fig. 2, h) — the centre of the Parkeria 



