46 Mr. H. J. Carter on the 



by equally minute, sparsely branched filaments (fig. 9, 5 5), 

 which may have extended itself throughout the Parkeria^ so 

 as to destroy by transformation the whole of the structure of 

 the latter and replace it by one which is totally different. 



That there are globular rhizopodous organisms similar in 

 outward form and equal in size to any Parheria existing at 

 the present clay may be learnt from what Mr. H. B. Brady, 

 F.R.S., &c., has stated in the description of his Siiringam- 

 ftiina fragillissima^ which was dredged by Mr. J. Murray in 

 the Faroe Channel during the cruise of H.M.S. ' Triton ' 

 ('Challenger' Reports, voh ix. "Text," p. 242), viz. :— 

 " Two specimens were secured, but owing to the excessively 

 fragile nature of the test both were much broken. The 

 largest fragment is represented in [his woodcut] figs, a, &, 

 drawn to the natural size. This specimen is about an inch 

 and a half (,'58 millim.) in diameter, and about eight tenths of 

 an inch (20 millim.) in thickness ; but it is probable that the 

 latter dimension may not be much more than half that of the 

 entire organism ; indeed, it is evident that the test, when 

 complete, was a rounded mass which, if developed with any 

 degree of symmetry, must have been a sphere about an inch 

 and a half in diameter." The structure revealed by the frac- 

 tured surfaces is that of a congeries of branching and inoscu- 

 lating tubes radiating from a common centre, " the walls of 

 wliich are composed of ' tine sand,' among which is a very 

 large number of minute foraminifera." 



To return to Parkeria. It is impossible to conceive that a 

 foreign nucleus could get into the centre and destroy its struc- 

 ture in a fossilized state ; but not so when it is remembered 

 that the Parkeria when fresh was probably as penetrable as 

 Mr. Brady's Byringammina fragillissima '^ further, that the 

 embryo of MiUarella might have previously existed in that 

 of the Parkeria, as in Prof. F. E. Schulze's specimen of 

 Spongelia imllescens which was infested with an Oscillaria^ 

 wherein the larva or ciliated ovum of the sponge already con- 

 tained several minute reproductive bits of the filament of this 

 Alga, of which, in 1878, he kindly sent me a mounted speci- 

 men (Zeitschrift f. wiss. Zool. Bd. xxxii. Taf. v. fig. 7). 



However, I had better describe a typical instance of this 

 kind of foreign nucleus in a specimen of Parkeria first, and 

 then leave the reader to form his own views as to how it 

 got there. Here the nucleus, which is in a specimen 

 of Parkeria about one inch and a half in diameter, passes 

 through its centre, so as to reach the circumference of the 

 Parkeria at opposite ends (PI. V. fig. 1, a). lu form it is a 

 conical solid cylinder, wdiose greatest thickness, viz. 9-24ths 



