Prof. (i. J. Allin;in on Polytrc;na iniiiiiK.-euni. 373 



Corals av the Polyzoa, until Carpenter, by the exanunation of 

 dried specimens received from tropical seas, determined its posi- 

 tion to be amon^- the Ivhizopoda — a determination subsequently 

 adopted by Max Scliultze, who, in a detailed memoir, takes a 

 similar view, arrived at from an examination of Mediterranean 

 specimens ])reserved in spirits. 



Having just had ample opportunity of examining it in a 

 living state, I am enabled to confirm in all essential points the 

 views of Carpenter and Scliultze. Po/i/tremn mintareum is a 

 true Rhizopod. Its calcareous skeleton forms a multitude of 

 irregularly superimposed chambers, which freely communicate 

 with one another by large orifices ; and besides the large 

 passages by which this free communication is maintained, the 

 walls of the chambers are almost everywhere traversed by 

 capillary canals. 



In the living state every chamber is filled with a clear 

 colourless protoplasm, so transparent that its presence may be 

 easily overlooked, until, by the action of alcohol or dilute acid, 

 it loses its transparency and becomes obvious. The proto- 

 plasm passes freely from chamber to chamber through the 

 wide passages by which the chambers open into one another, 

 Avhile it also sends delicate prolongations into the capillary 

 canals of the walls. I can confirm Max Schultze's observa- 

 tion of the existence of siliceous spicula, resembling those of 

 sponges, in the interior of the chambers ; but as in many 

 specimens I could find no trace of them, I can hardly avoid 

 regarding their presence as accidental. 



Though there can thus be no doubt of the rhizopodous na- 

 ture of Pohftrema^ I never succeeded in detecting the emission 

 of pseudopodial extensions of the protoplasm ; and the capil- 

 lary processes which may be traced into the canals of the 

 chamber-walls were never, during prolonged examination of 

 living specimens, projected beyond the surface. 



Any contribution to our knowledge of Polytrema will pro- 

 bably be deemed of interest, more especially when we regard 

 the apparent affinities of Polytrema with Eozoon, and the light 

 which the structure of the living Rhizopod seems capable of 

 throwing on the oldest of known organisms. 



I remain, Gentlemen, 



Yours faithfully, 



Mentone, Alpes Mari times. GeORGE J. AlLMAX. 



April 2, 1870. 



Ann. d: Mag. X. Hist. Ser.4. TV. v. 26 



