M. Otto Halm on Eozoon canadense. 269 



lip of a number of coherent segments, wliicli have only 

 undergone a partial separation ; these appear to have ex- 

 tended themselves horizontally without any definite limit ; 

 but have here and there developed new segments in a vertical 

 direction, so as to give origin to new layers. In the spaces 

 between these successive layers, which were originally occupied 

 by calcareous shell, we see the ' internal casts ' of the branch- 

 ing canal-system, which give us the exact models of the ex- 

 tensions of the sarcode-body that originally passed into them. 

 But this is not all. In specimens in which the Nummuline 

 layer constituting the ' proper Avail ' of the chambers was 

 originally well preserved, and in 'wdiich the decalcifying pro- 

 cess has been carefully managed (so as not by too rapid evo- 

 lution of carbonic-acid gas to disturb the arrangement of the 

 serpentinous residuum), that layer is represented by a thin 

 white film covering the exposed surfaces of the segments, the 

 superficial aspect of which as Avell as its sectional view are 

 shown in fig. 2. And when this layer is examined with a' 

 sufficient magnifying-power, it is found to consist of extremely 

 minute needle-like fibres of serpentine, Avhich sometimes stand 

 upright, parallel, and almost in contact with each other, like 

 the fibres of asbestos (so that the film which they form has 

 been termed the ' asbestiform layer '), but which are frequently 

 grouped in converging brush-like bundles, so as to be very 

 close to each other in certain spots at the surface of the film, 

 whilst widely separated in others. Now these fibres, which 

 are less than 1-1 0,000th of an inch in diameter, are the 

 ' internal casts ' of the tubuli of the Niuiumiline layer (a pre- 

 cise parallel to them being presented in the ' internal cast ' 

 of a recent Amphtstegina in the author's possession) ; and their 

 arrangement presents all the varieties Avhich have been de- 

 scribed ( § 391) as existing in the shells of Opercxdina. Thus 

 these delicate and beautiful siliceous fibres represent those 

 pseudopodial threads of sarcode, which originally traversed the 

 minutely tubular walls of the chambers ; and a livecise model 

 of the most ancient animal of Avhich we have any knowledge, 

 notAvithstanding the extreme softness and tenuity of its sub- 

 stance, is thus presented to us Avith a completeness Avliich is 

 scarcely even approached in any later fossil. 



" § 399. In the upper part of the ' decalcified ' specimen 

 shown in fig. 2, it is to be observed that the segments are con- 

 fusedly heaped together, instead of being regularly arranged 

 in layers, the lamellafed mode of groAvth having given place 

 to the acervuJine. This change is by no means uncoiinnon 

 among Foraminifera ; an irregular pi ling- together of the 

 chambers being frequently met Avith in the later growth of 



