EORAMINIFERA PROM THE NORTH ATLANTIC AND ARCTIC OCEANS. 
361 
To us it appears that the Polythalamous Foraminifera are often, if not generally, vivi- 
parous, and that the young shell, when hatched, consists of two chambers. We think 
that the subsequent chambers of these Polythalamians are not always formed slowly, 
one by one, but sometimes, at least, laid down, and marked off by the growth of two or 
more septa, at the same time; calcification beginning at points nearest to the earlier 
chambers, the thickness of the chamber-wall being in direct ratio with its age. This 
mode of growth of more than one chamber at a time seems to be proved by the curious 
manner in which the sarcode passes, by many bundles, from the older chambers into 
the newest in those individuals of Polymorphina lacteco which throw out tubular stag- 
horn processes from their last chamber (P. tuhulosci , D’Orb.); for, as may be seen in fig. 52, 
the newest chamber, namely, that which bears the cervicorn appendage, communicates, 
not merely with the ante-penultimate chamber, but, by a double row of lateral apertures, 
with all the chambers occurring on its own side, namely those which it overlaps. The 
communication of the last, outer, wild-growing chamber with the penultimate is not 
only by means of this double row of apertures, but (as is seen in fig. 52 b) by the ordi- 
nary radiated mouth. Another view, however, may be taken of the growth of such an 
individual as fig. 52 : thus, we may suppose that absorption has taken place, opening 
foraminal communications between the last and the former chambers. Either hypo- 
thesis would explain the fact, — that, as we find on breaking open very large specimens 
of the normal P. lactea , the stolon-passages between the older chambers are very free and 
patulous ; whereas the terminal mouth of the last chamber presents the radiate condi- 
tion; the only passage here for the sarcode being the thin slits around the strong 
growth of hyaline shelly matter in the mouth. 
Fig. 45 represents the group of individuals to which D’Orbigny applied the sub- 
generic term Globulinci ; but neither this term nor that of Guttulina (another so-called 
subgenus) can be separated from the ordinary, more or less oval, more or less pyriform, 
or more or less elongate varieties of Polymorphina lactea. 
Figs. 45 & 46 are from the Hunde Islands (Dr. Sutherland), in three dredgings from 
25-70 fathoms. Rather common and of small size. Also from the Norway coast 
(Mac Andrew and Barrett) in the mixed sands. 
Polymorphina lactea , Walker and Jacob, Yar. compressa, D’Orbig. Plate XIII. figs. 
47-51 (Arctic). 
These are more or less flattened forms, ranging themselves around P. compressa , D’Orb. 
(For. Foss. Vien. pi. 12. figs. 32-34), though not exactly identical with that variety of 
P. lactea. In the relative length of the chambers, their setting on, and in the degree 
of exposure of the plaiting by the alternation of the double series of chambers, these 
Po lymorp bin m are so very variable, that we have taken the flattened condition as a 
characteristic, and out of the very many names they have received, we have chosen 
“ P. compressa ” as a secondary centre around which to collect a certain series of more 
or less elongate and compressed forms, more elongate than P. lactea proper, and less 
