388 PEOF. ALLMAN ON THE EECENT KESEABCHES 



class. To this class Hertwig, in his most recent memoir*, has 

 assigned the name of TMlmnopJiora. 



The researches which have thus from various quarters been 

 brought to bear on these organisms have made known to us many 

 new facts, and enable us to give a more complete picture of them 

 than had been hitherto possible. 



The Thalamophora are organisms whose soft bodies are formed of 

 sarcode or protoplasm which envelopes one or more nuclei, and which 

 for the purposes of locomotion and the prehension of nutriment has 

 the power of emitting pseudopodia. Receptacles of liquid in the 

 form either of contractile or of non- contractile vacuoles are almost 

 always present. All Thalamophora are enveloped by a shell or 

 test, which is either purely chitinous or is hardened by calcareous 

 deposits, or inerusted by siliceous fragments. In its shape it 

 belongs to the "monaxial fundamental form " of Haeckel, having 

 a main axis, at one extremity of which is the oral orifice of the 

 test. In the simplest cases this main axis is straight {Gromia, 

 Microgromia, Euglypha, Nodosaria, &c,), but in most of the marine 

 forms it is regularly curved in a spiral (Miliola, Hotalia, Poly- 

 stomella, &c.), while in some the regular curvature is masked by a 

 subsequent irregularity of growth. 



In this monaxial shape and in the constant position of the oral 

 orifice of the test in relation to the main axis we find the essential 

 character by which the Thalamophora are distinguished from the 

 Heliosoa. These, instead of being monaxial, are " homaxial " 

 (Haeckel) ; that is, all their axes being of equal value, their proper 

 form is that of the sphere. Further, when a test is present in 

 the Heliozoa, this has either no constant opening, or the openings 

 are numerous and placed without any definite relation to an axis. 



By consecutive constrictions of the test at right angles to the 

 main axis polythalamic forms are produced. Carpenter had already 

 shown that the characters derived from the polythalamic or mono- 

 thalamic condition of the shell are of but slight systematic value ; 

 and this view is fully borne out by the most recent researches, 

 which make it evident that the number of the nuclei in the Eora- 

 minifera do not stand in any direct relation to the number of the 

 chambers — in other words, that each newly formed chamber does 

 not necessarily contain a newly formed nucleus. The polythalamic 

 forms therefore are not be regarded as colonies of monothalamic 

 forms. 



* Op. fit. Jenaisehe Zeitschrift, 1876. 



