422 



KNOWLEDGE. 



November, 1910. 



the Hyaline groups which habitually mask the 

 external characteristics of their shells by the 

 addition of an external coating of sand-grains or 

 mud. These species are to all external purposes 

 Arenaceous Foraminifera. but their true position 

 in the Order is immediately recognisable if a thin 

 section of the shell is made, as the charac- 

 teristic shell wall can alwavs be detected under 

 the external coating. It is not surprising therefore 

 that among the manv schemes of classification which 

 have at various times been proposed for the 

 Foraminifera, there are several in which no essential 

 \-alue has been attributed to the agglutinated shell, 

 such species being allotted indifferently to either the 

 Imperforate or the Perforate group, according to 

 their external resemblance to recognised types, or the 

 caprice of the author w here no superficial resemblance 

 existed. Such schemfs of classification, so far from 

 solving the (juestion of the zoological value of the 

 group, appear to increase its difficults", for while there 

 are some trulv .\renaceous Foraminifera which bear 

 a close external resemblance to Imperforate species. 

 and a great man\- more w hich are isomorphous w ith 

 Perforate types, there are a still greater number 

 ^\■hich ha\-e no particular resemblance to generic 

 types in either group. 



In Bradx's sx'stem of classification, which is more 

 or less generally accepted as the most convenient in 

 our present state of knowledge of the Order, the 

 external investment of the animal is abandoned as 

 an exclusive basis for a primary division ; that is to 

 say, such species as possess an internal shell, masked 

 by an agglutinated test, are allotted to the Imperforate 

 or Perforate group, according to the nature of the 

 internal shell. The truly Arenaceous Foraminifera, 

 that is to say, those in which the shell consists en- 

 tirely of adventitious material fastened together \\ ith 

 either a chitinous or ferruginous cement, are sepa- 

 rated into two distinct families, (i) the Astrorhizidae, 

 nearly all of which are deep-sea forms, characterised 

 by large irregular and usualh- monothalamous shells, 

 sometimes branching or radiate, and segmented b\- 

 constrictions of the wall, but never truly septate or 

 symmetrical : and (ii) the Lituolidae in which the 

 chambers are usually regular. Many of the Lituolidae 

 are isomorphous with porcellanous and hyaline types. 

 The species treated in this paper are Lituolids. 



The origin of the .Arenaceous Foraminifera is yer\- 

 uncertain. Neuma^r, Lister and others suppose that 

 they represent more primitive types than the 

 Imperforate and Perforate groups. But the 

 evidence in either direction is ver\- fragmentary 

 and to our ideas it seems more probable that they 

 are of later evolution than the shell-secrc-ting forms. 

 The facts on which we base our belief are as 

 follows : — 



(Ij The power of secreting carbonate of lime is 



generalh' present in animal organisms and does not 

 mark an advance on the selection of foreign material 

 but rather the contrary. 



(2) The geological record does not show that 

 .Arenaceous Foraminifera preceded the other groups. 

 So far from this being the case, the earliest 

 known Foraminifc-ra deposits contain Perforate 

 types only. 



(3) The "selective power" exercised by many of 

 the .Arenaceous P"oraminifera in the construction of 

 their shells is. in our opinion, evidence that the 

 animals possess functions and powers greath' in 

 advance of their relatives of the shell-secreting 

 types. 



The possession of " selective power " b_\- certain 

 species has long been known, but the subject appears 

 to have been avoided by most rhizopodists, probably 

 owing to the difficulty of explaining a process w hich 

 seems to require the possession of " intelligence " b\' 

 organisms w hich, as we know, are merely particles of 

 nucleated protoplasm possessing no differentiated 

 organs of an\- kind. We are not ourselves prepared 

 to furnish an\' explanation of the phenomena, nor do 

 we expect any explanation to be forthcoming in our 

 present state of ignorance as to the life-history of 

 these organisms, but we have in another paper* 

 attempted a short study of this most suggestive 

 subject. Space will not p<;rmit of any detailed 

 reference to the facts which wc have there set forth, 

 but the student interested in the subject will find in 

 that paper ample e\-idence that these little organisms 

 (Protozoa) are endowed with a power of selection 

 and adaptation of adventitious material, both for 

 purposes of construction and defence, equal to 

 an\'thing which exists among the higher forms of 

 life (Metazoa). 



To return to the immediate subject of our paper, 

 the first species, f/i?^/«/'/n-ir,i,'/;;/;//« iiggliitiiuiiis, ca.nnot 

 be described as a common British species, for the 

 records of its occurrence appear to be limited to the 

 Isle of \\'ight (Millett) and the East Solent (Brady) 

 and two dredgings in the Irish Sea (Balkwill and 

 \\'right). We believe, however, from our observa- 

 tions that this rarit\- is possibly due to the fact that 

 the cement with which the shell is built up. is when 

 dried, extremely friable, so that the shells break up 

 in the process of cleaning the material. It is, more- 

 over, as we have remarked in the paper already 

 referred to. a species which, occasionally at an}- 

 rate, exercises a fantastic taste in the selection of its 

 building material, selecting grains of marked contrast 

 in colour for the construction of its shell, in prefer- 

 ence to the quartz sand among which it lives. 



Haplophriii^iiiiimi ii<:;}^lufiihiiis. as w ill be seen from 

 our Figure 1, commences life with a series of 

 chambers arranged in a spiral coil ; then departing 



'■' Edward Heron-Allen and Arthur Earland " On a new species of TechnitcUa from the North Sea, with some observations 

 upon selective power as exercised by certain species of .Arenaceous Foraminifera." Journal Ouekett Microscopical 



Club, 1900, pp. 403-412. Plates 31-35. 



