648 MR. R. J. LECHMERE GTJPPY ON SOME [K~OV. 6, 



that " they exhibit an early condition of Polymorphina, in which 

 we see an entosolenia, slightly modified, playing the part of the 

 primordial chamber of this form. This entosolenian condition of 

 Polymorphina is nearly always apparent in specimens sufficiently 

 small or nnadvanced to leave the early chambers translucent and 



open to examination As they advance in growth the 



individual Polymorphina} are invested with additional chambers 

 after a type peculiar to themselves, but in a very irregular manner 

 as regards the capacity and shape of the chambers." 



If such a unicellular Polymorphina as the one shown in my 

 fig. 7, or in Parker and Jones's figure just referred to, takes on 

 additional chambers in a regular series on one side only instead 

 of alternately on different faces of the shell, it becomes a 

 Cristellaria either straight, curved, or involute. In further explan- 

 ation it may be stated that in Polymorphina the chambers are de- 

 veloped alongside of, and adherent to, each other and the primordial 

 chamber like drops of resin which have exuded from a tree. But 

 if the chambers are developed in a single symmetrical and regular 

 series, straight or curved, each segment being developed from and 

 adherent to the preceding one only, the organism is a Cristellaria, 

 and so may attain a considerable development in this shape. The 

 Cristellariau segments are added consecutively on one side only of 

 the previous segment, and may be represented as one of the 

 branches of a letter V inverted, the aperture being at the one end 

 (the apex) of the V : the other branch, in the case of a true 

 Cristellaria, not being developed. If, however, at a certain stage, 

 the other branch of the V becomes developed, the previous segment 

 being embraced, not on one side only, as in the Cristellariau form, 

 but on both sides, and the aperture being at the apex, we have a 

 Plabelline Frondicularia. In this form, generally speaking, the 

 segments are extremely compressed, the whole test being scarcely 

 as thick as ordinary paper. 



In fig. 1 (Plate XLI.) we have a shell with a Cristellarian 

 beginning, passing into a Kodosaria. This may be called 

 the Amphycoryne-iorva of Nodosaria, just as the specimen de- 

 lineated in fig. 3 may be called the Flabellina-i orm of Frondicu- 

 laria. The specimens figured illustrate the development of the 

 genera to which we give the names of Frondicularia and Nodosaria, 

 and suggest the conclusion that the primordial forms from which 

 they were evolved resembled a Lagena and that the next steps of 

 the evolution were represented by Polymorphina and Cristellaria. 

 Frondicularia is no doubt the next step in one direction : whilst 

 in another the evolution takes the line of Nodosaria. Hence it 

 appears that Nodosaria is not directly developed from Lagena. 

 The generic forms called Polymorphina, Uvigerina, and Sagrina 

 intervene. We have thus an explanation of facts hitherto not 

 quite easily explicable, namely, for example, the development of 

 many Poraminifera from a more complex (biserial, triserial) form to 

 a simpler (uniserial) form. In most individuals belonging to 

 genera such as Frondicularia and others of the Nodosarian series 



