KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 25. N:0 9. 7 



It must, however, be borne in raind, that the smallest embryo segments not alwajs 

 give 1'ise to a dimorphous colony, but at once assume the mature arrangement of the 

 segments. Sucli forms are often apt to a pygmean growth. The same mode of evolution 

 in other genera, particularly in Miliolina, has been made the object of most painstaking 

 researches by the experienced Rhizopodologist M. Schlumberger, who with the utmost 

 skill and sedulity, in numerous papers ' — mostly during the last seven years published in 

 the Mémoires and Bulletins de la Société Zoologique de France and in Mémoires de la 

 Société géologique de France — has produced masses of examples of this evolutional pro- 

 cess in some Miliolince. In these excellent expositions it is stated, that the smallest prim- 

 ordial segments give rise to a larval stage generally of quinqueloculine arrangement of 

 the segments, often succeeded by a trilomline development, whereupon foUows the ma- 

 ture biloculine condition. 



Instances of a total triloculine larval stage will also be met with, being a shorter 

 step to the fuUy developed biloculine stage. The initial segment in such forms is gene- 

 rally somewhat larger than in the last mentioned forms. 



As in the instances of polymorphism in Frondicularia the differences in the arran- 

 gement and number of segments in the larval stage are subject to great variation, so raay 

 also the polymorphism in the Miliolince be looked upon as vacillating gradations of 

 evolution, which cannot afford satisfactory distinctions for establishing species; and that so 

 much the less, when we consider, that initial segments with dififerent power of growth are» 

 as stated above, produced by one and the same individual segment. An arrangement of 

 the larval segments may in several instances appear as being directed by a clear mathe- 

 matical rule, but which at another time will be eclipsed by irregularities and exceptions. ^ 



To show how little attention has been paid to these facts even by reputed Rhizo- 

 podologists I will reproduce some of v. Reuss' designations amongst an assemblage of 

 Nodosarina communis d'Orb, with varieties, depicted by v. Schlicht in his valuable me- 

 moir, the Foraminiferen des Septarienthones von Pietzpuhl 1870 (Wien Ak. S. Ber. 62, p. 455). 



To any one experienced in dealiiig with this categorj^ of organic forms it will be 

 obvious, that all the foi-ms here (Fig. II) represented from fig. 1 to lig. 22 must be grouped 

 under Nodos. communis d'Orb. var. consohrina d'Orb. (a denomination, which will be better 

 substituted bj^ ^^pauperata" d'Or.b. the nomen triviale " consobrifia" being superfluous). As 

 usually the segments of the more developed stages become more or less inflated and 

 present constricted sutures. 



Fig. 23 — 26 represent forms approaching Nod. Boueana, ovicula d'Orb. and per- 

 haps the allied farcimen Sold. but may also be considered as a feeble form of the preceding. 



Fig. 27 — 34 are forms of N. communis d'Orb. and not distinct from Nod. Roemeri 

 and mucronata Neugeb. 



' Por the coiirteous corarnunication of his raemoirs I have to acknowledge in_y great obligations to 

 the aiithor. Valuable informations and suggestions on this subject have also been advaiiced by Van den Broeck 

 in Bull. E. Soc. Malac. Beige (1893), 28: and in Bull. Soc. Beige Geol. (1893), 7. For transmission of his 

 able papers I stånd under great obligation to this author. 



- Por a fuller -account of the "diraorphisra" see nij' paper "Oni den sä kallade verkliga diamorfismen hos 

 Rhizopoda reticulata" 1889, Bih. till K. Sv. Vet. Ak. Handl. 15. 4, No. 2. 



