Mr. H. J. Carter on the Polytremata, 205 



of one of my specimens, close to its circumference, on the 

 shell of the bivalve to which it had adhered, and had become 

 developed under the protection of a projecting lamina of the 

 shell. Hiis, which is conical and, when first examined in 

 situ, upright, presented a single large aperture of a spiral form 

 in the summit, was afterwards removed by a hair pencil and 

 mounted in balsam, where, falling on its side, the aperture of 

 course became undistinguishable, while the body generally pre- 

 sented an elongated conical form about l-92nd inch long, and 

 l-138th inch broad at the base (fig. 8). 



On examining this with a |-inch object-glass and trans- 

 mitted light, it appears to consist of a transparent yellowish 

 envelope of a chitinous aspect (fig. 8, c), in the interior of 

 which is a cylindrical conical cavity extending downwards 

 from the aperture at the summit to near the bottom of the 

 base, surrounded throughout by minute granular ojDaque 

 material (fig. 8,^). 



The envelope (fig. 8, c) is very irregular in its outline, and, ' 

 besides the large aperture at the summit (fig. 8, «), presents an 

 appearance of several smaller ones on the sides at the ends of 

 conical or wart-like processes respectively (fig. 8, ee), out of 

 one of which projects a minute filament of prohably foreign 

 material (fig. 8,y). At the base it is spread out irregularly, 

 being deflected or prolonged in one direction much more than 

 in any other (fig. 8, Z*), while its surface is microscopically gra- 

 nulated throughout, barely visible with the power mentioned. 



The cavity (fig. 8,^) is, as before stated, cylindrical, appa- 

 rently corrugated in a spiral manner at its upper part, widest' 

 where it ends in the aperture at the summit, and narrowed to 

 a point at the other extremity, where it appears to be turned 

 towards the deflection of the base. 



Lastly, the minute granular opaque material which surrounds 

 the cavity appears to be arranged in pouch-like aggregations. 



Thus the embryo of Polytrema halaniforme ( = Carpenteria) , 

 if this be one (and there does not appear to me to be any 

 reasonable doubt on the subject), does not begin in the form 

 of a " Globigerine type of Foraminifera " approximating 

 '' closest to Rotalia^'' as stated by Dr. Carpenter {op. cit. 

 p. 188), unless the lohed form of the supposed embryos in 

 the broken chambers above mentioned be considered as such ; 

 but then the smaller ones, which have been viewed as the pre- 

 ceding stage of development, are unlohed^ and all have the 

 apparent aperture superior and apical as in P. halaniforme^ not 

 inferior and basal as in Rotalina. In short, we do not yet know 

 the embryonic form which the ovum of either Polytrema hala- 

 niforme or P. miniaceum first takes, any more than we know the 



