490 Mr. Joseph Jackson Lister [Feb. 15, 



dissolving the shell it will be found to be filled by protoplasm ; there 

 are no muscles, brain, stomach, or other organs. All the fuuctions 

 are here, as in Protozoa in general, performed by undifferentiated 

 protoplasm. 



The simple character of the soft parts was discovered in 1835 by 

 Dujardin — who pointed out the alliance of Foraminifera, not with 

 Cephalopoda but with Amceha, and proposed the name Rhizopoda 

 still in use. ^ 



One of the commonest littoral species is Polystomella crispa. The 

 shell of this will usually be found to have the following structure. 



[A lantern slide showing the shell of this species in lateral and 

 anterior aspects was here shown.] 



A biconvex shell, symmetrical about a median plane, keeled, the 

 chambers arranged in a spiral — each convex anteriorly, i.e. towards the 

 terminal face. The alar prolongations — each chamber set astride of 

 the next inner whorl ; thus the last whorl hides all its predecessors. 

 The V-shaped row of terminal pores — the main opening to the exte- 

 rior. Each chamber has been in its turn the terminal chamber. As 

 we trace them back through the spiral series the number of the canals 

 between the chambers, which open by these pores, becomes smaller, till, 

 as we approach the beginning, there is only a single canal. In speci- 

 mens of this type a large globular chamber occupies the middle, this is 

 followed by a second chamber of characteristic shape, to which the 

 spiral series succeeds. 



The outer walls are traversed by minute pores. There is also a 

 canal system lying in the thickness of the walls. 



In the earliest stage the organism consisted of a single chamber, 

 and its shape, at successive stages of growth, is preserved in the inte- 

 rior of the shell. 



Foraminifera live from shore pools to great depths, from arctic to 

 tropical waters. A small group is pelagic, living in surface waters, 

 down to at least 500 fms. 



Their empty shells constitute the bulk of the " Globigerina ooze," 

 which forms the floor of the ocean in many tropical and temperate 

 regions. 



[Two lantern slides were here displayed, showing the character 

 of floatings from the ooze obtained by H.M.S. ' Challenger,' east of 

 the Crozet Islands, in 1375 fms., and north of Ascension Islands in 

 2350 fms. respectively. The former mainly consisted of Globif/erina, 

 the latter largely of Pidvwiilina, and attention was called to the eroded 

 condition of the shells in the latter, a characteristic of the ooze from 

 depths approaching 2400 fms., l)eyond which all calcareous organisms 

 are dissolved.] 



Foraminifera abound in many geological deposits, back to the 

 Palaeozoic period. We thus have an added dimension in which to 

 project our ideas of their evolution. 



The recent advances in our knowledge of their life history began 



