CARPENTER ON THE STUDY OE THE FORAMINIFERA. 
327 
Excepting a, few arenaceous forms, to which we shall presently 
refer, the shell is of all other Foraminiferci calcareous, and, as Professor 
Williamson has shown, presents two well-marked modifications of 
texture, the ‘ porcellanous,’ and the ‘ vitreous.’ 
Among the porcellanous forms no minute structure whatever has 
been observed, either in the substance of the shell itself, or of such 
projections as may arise to diversify its surface. The shell is opaque- 
white w T hen seen by reflected light. “ When this natural or arti- 
“ fieial laminae of it, however, are viewed with transmitted light, the 
“ opacity gives place to a rich brown or amber colour, which seems 
“ to be imparted by the animal matter that is united with the calci- 
“ fying deposit, the colour of the sarcode body being usually the 
“ same as that of the shell. In a few instances both the shell and 
“ animal body have a rich crimson hue.” Decalcification by dilute 
acids leaves behind a thin fibre of gelatinous matter, “ very distinct 
“ in its aspect from the sarcode-body which the shell included.” 
“ In the shells of the vitreous or hyaline type, on the other hand, 
“ the proper shell-sub stance has an almost glassy transparency; which 
“ is shown by it alike in the thin natural laminae of young speci- 
“ mens and in artificially-prepared sections of such as are thicker 
“ and older. It is usually colourless, even when (as is often the case 
“ with Botaliee) the substance of the animal is deeply coloured. In 
“ certain aberrant forms of the Eotaline type, however, we shall see 
“ that the shell is commonly, like the animal body, of a rich crimson 
“ hue. But notwithstanding the transparence of their substance, 
“ these shells derive an adventitious opacity from being channelled. 
“ out more or less minutely by tubular perforations, which, when 
“ occupied either by air or by any substance having a refractive 
“ power different from that of the surrounding shell, interfere with 
“ its power of transmitting light, and cause it to reflect a large part 
i% of that which falls upon it. Their effect varies, however, according 
“ to their degree of minuteness and the closeness of their arrange- 
“ ment.” In Rotalia the average diameter of these perforations is 
about l-3000th, in Globigerina it varies from 1-10,000th to l-5000th 
that of Dr. Carpenter in the view which he takes of the nearer affinities both of 
the Actinophryds and Polycystina. The former he associates in one order (Pro- 
teina) with the Lagynidce and Amcebina; the latter in a second (IIerpnemata) with 
the Gromida and Poramimfera. The remaining Radiolarian Rliizopods, along with 
“ certain allied bnt heretofore imperfectly understood pelagic genera,” are placed in 
a third order (Protodermata). Dr. Wallich’s arrangement may very briefly be 
expressed as follows :— 
Nucleus distinct. \ Profttoa. j A contractile vesicle. 
C_ 2. Protodermata. 
Nuclear granules diffused. j 3. Herpnemata. ^ No connactile vesicle. 
Here the Orders follow according to their rank, the highest being first placed. 
So that, as regards the relative grade of the principal Rhizopod families, the two 
systems essentially agree. 
