rORAMINIFER A— HERON- ALLEN AND EA INLAND. 225 



Whether there is any tiue symbiosis between Polytrema and Sponges we are 

 unable to say, but specimens have been found in which the whole of the outer 

 surface was furry with mmute projecting spicules. The Sponge, if incrusting the 

 Polytrema, must have been in an infinitely thin layer ; it seems possible therefore 

 that the sponge-tissue and the protoplasm of the Polytrema may have been 

 intermingled under the outer shell-surface. Other specimens were seen in which 

 a Sponge with large, strong, projecting spicules was living in association with 

 Polytrema, at any rate to the extent that the two organisms were close together 

 and approximately the same size (Fig. 31). With such a rapidly-growing organism 

 as Polytrema it is fairly evident that at the next stage the spreading chambers 

 would envelop the Sponge. If symbiosis did not then occur, the large number of 

 strong spicules enclosed in the Pohjtrema would be analogous to those highly- 

 spiculiferous specimens which have occasioned so much controversy in the past. 



Several specimens exhibit evidence that the greater part of -the internal 

 structure has been eaten out by another organism, leaving a more or less spherical 

 cavity. Of the nature of this enemy we have no evidence, but, starting from the 

 surface of the trunk it apparently tmmels into the thickest part of the shell, 

 often hollowing out the interior of the trunk right down to the base (Figs. 23, 24). 



Polytrema, like most, if not all, other Foraminifera, has a chitinous membrane 

 lining the shell-wall. This is exceptionally thick in the earliest (Figs. 27, 28, 30), 

 and consequently the oldest, chambers, becoming very delicate in the extended arms. 



The general form of the N.Z. specimens is erect and branching, but de- 

 pressed and squamous forms, so common in the Mediterranean, also occur. The 

 colour is pale : no highly-colom'ed individuals were observed. It varies from pale 

 pink to very faint flesh-colour, practically indistinguishable from the var. alba 

 (Carter). The nature of the preservatives employed may be partially responsible 

 for this. 



As above indicated, the exhaustive examination of the Corsican material has 

 served to confirm all the points upon which we have laid stress in discussing 

 the " Terra Nova " material, including the normal occurrence of a microspheric 

 type commencing its existence as a minute sessile truncatuline individual. The 

 Corsican material presents several minor points of distinction as compared with 

 the " Terra Nova "' gatherings. 



1. The early free stage is much more abundant and the individual specimens 

 attain a nnich larger size and more advanced development than in N.Z. 



2. The colour variation is much wider, ranging between the most vivid 

 blood-red and pure white. This may be partly due to the freshness of the 

 Corsican material, as the colouring matter of Polytrema is unquestionably more 

 or less fugitive. 



3. The Corsican specimens are of a more massive type than those from N.Z., 

 and delicately branching individuals are comparatively rare. This is probably 



VOL. VI. 2 G 



