FoYaminifera from the Coast of Norway. 275 



size, thickness, ornamentation, &c. Mostly cosmopolite, they 

 present species that have individuals both in shallow and in 

 deep seas, in brackish and in salt water, within the Arctic Circle 

 and at the Equator; and consequently one form will be repre- 

 sented by thin-shelled and by thick-shelled individuals, by smooth 

 and rough, by convex and flat, and by infinitely small and com- 

 paratively monster specimens. 



Further, to enter into details, the individual parts of a Fora- 

 minifer may be seen, in different individuals specifically allied, to 

 have very various proportions of size. The primordial chamber 

 may be either extremely small or largely distended, — the smallest 

 or the largest in the whole shell : the succeeding chambers may 

 be short and globular, or elongated and narj-ow : the exogenous 

 growths of shelly matter may be delicately distributed in lines 

 and points, or coarsely agglomerated, masking a whole surface ; 

 they may be nearly absent in one, and forming a serrated or an 

 entire wing or keel in another : the shell may be in one group 

 hyaline or sandy ; in another, it may be white and opake, or 

 coloured and gritty : the small shells, indeed, are usually smooth, 

 the larger ones often coarse or sandy. 



Not only do the individuals of a species present frequent dif- 

 ferences in the relative proportions of their chambers, and in the 

 degrees of thickness of the shell-walls, according to certain re- 

 cognizable conditions of habitat, &c., but there are also to be 

 found still further departures from a determinate type, — always, 

 however, within certain specific limits; when, for instance, a 

 Nautiloid form takes on a rectilinear growth ; or, vice versa, a 

 Stichostegian is partially curved ; or when a cycloidal growth is 

 in part replaced by a spiral ; or the opposite. 



We need not here do more than allude to the interesting branch 

 of research in the relations of these lowly-classed creatures which 

 has reference to the representative forms which they continually 

 exhibit, both amongst themselves and with respect to higher 

 groups of shelled animals. Not only do the varieties of one 

 species exhibit peculiarities of form which are more especially 

 characteristic of other and definite species, but the Foraminifera 

 present remarkable mimetic resemblances to the various Mol- 

 lusca and Molluscan groups; thus, for instance, we see the 

 straight and variously-curled Cejihalopoda (including the fossil 

 forms) markedly imitated by the Foraminifera. 



With regard to the nomenclature of this widely-diffused group, 

 a certain licence must be allowed in the use of binomial terms 

 for some and not a few forms, which are physiologically varieties, 

 however protean and distant from the specific type, and have no 

 strict title to a separate place in the list of species. Many spe- 

 cies, however, present such numerous varieties of form, ranging 



18* 



