86 Transactions of the Royal Microscopical Society. 



pared with the susceptibility of living on under very various 

 conditions, shown by man, the dog, &c., but, of course, the terms 

 of comparison are not really equal. The extreme variability of 

 Foraminifera, of both great groups (Porcellanous and Vitreous), is 

 doubtless governed by some systematic life-properties which we do 

 not at present recognize in their totality. A wide field for research 

 opens here. As far as we can see at present, as far as we understand 

 the nature and growth of these Microzoa, there seem to be but 

 relatively few links wanting to make the gradations, from one group 

 to another, in form and structure, so evident and so close that all 

 the Foraminifera might be placed in the close union of a specific 

 group, modified by conditions of habitat, feeding, climate, and 

 hereditary peculiarities of growth. But I am not yet prepared to 

 avow a behef in their unispecific relationship. 



RemarTis on the Cristellarians figured in Plates CXXVIII. and 

 CXXIX. in illustration of their Variability of Form and 

 Ornament. 



Taking examples, as much as possible, from among contempo- 

 raneous and local groups, we have the associated forms,. whether 

 varying from an original stock by long series of differences, in 

 collateral races, or showing new varieties, resulting from the 

 peculiar conditions of place and time. 



The beautiful illustrations of Herr Max von Hantken's Mono- 

 graph* on the Foraminifera of those Tertiary strata in Central 

 Hungary, which he terms the "Clavulinaf Szaboi-beds," supply us 

 with a fine series of variations of well-known forms from one geo- 

 logical deposit. 



Alcide D'Orbigny's Monograph on the Tertiary Foraminifera 

 of Vienna, known to all Rhizopodists, has also been applied to for 

 some good typical forms. Thirdly, the Liassic and Lower Oolitic 

 Foraminifera, with their innumerable variations of Nodosarinw, 

 illustrated by M. 0. Terquem and Mr. H. B. Brady, F.E.S., supply 

 us with two sets of Ehizopods living about the same time and 

 having similar developments. 



The few figures taken from the reduced outlines of some 

 of Soldani's illustrated Italian Tertiary (Pliocene) Foraminifera, 

 belong to forms not very far removed in time from those figured by 

 D'OrlDigny and Von Hantken (Miocene). 



Fig. 1 (PI. CXXVIII.) is one of the simplest forms oiNodosarina 

 {Nodosaria proper). In Fjg. 2 it is no longer quite straight, but 



* From the ' Mittheilungen aiis dem Jahrbuche der kon. img. geologischen 

 Anstalt,' vol. iv., 8vo. Budapest, 1875. 



t The term Cluvulina is here applied to the elongated Tritaxia (Rcuss), or 

 dimorphous VcrHcxiilina, D'Orb., allied to Clatulina communis, D'Orb. 



