185 



passages and large openings in the partition walls. In like manner 

 those portions of the living sarcode body which are enclosed in the 

 individual chambers are in direct communication with one another 

 by means of processes which pass through the passages and openings 

 in the septa, and connect one portion with another. The quality of 

 the body-substance, the mode of movement and nourishment, agree 

 closely with those which have been depicted as characteristic of the 

 order. Our knowledge of the mode of reproduction is imperfect. 

 Amongst the forms without a shell, fission has been observed as well 

 as fusion, which may perhaps be referred to a species of sexual 

 reproduction (conjugation). The reproduction of shell-bearing 

 Poraminifera such as Miliola and Rotalia has also been observed. 

 The former produces from the protoplasm, of its body single 

 chambered, the latter three-chambered, young. Probably this mode 

 of reproduction is preceded by an increase in the number of nuclei, 

 and the animal divides into as many portions as there are nuclei, 

 each of which becomes a young Foraminifer, and contains but one 

 nucleus. 



In spite of their small size, the shells of our simple organisms may 

 lay claim to no small consequence, since they not only accumulate in 

 enormous quantity in the sea sand (M. Schultze* calculated their 

 number for an ounce of sea sand from Molo di Gae'ta at about one and a 

 half millions), but are also found as fossils in different formations (the 

 cretaceous and tertiary), and have yielded an essential material to the 

 construe :ion of rocks. Silicious nodules of Polythalamia are ever; 

 found in Silurian deposits. The most remarkable, on account of 

 their considerable size, are the Nummulites (fig. 124) in the thick 

 formation of the so-called ISTummulite limestono (Pyrenees). A coarse 

 chalk of the Paris basin, which makes a : excellent building stone, 

 contains the Triloculina trigonula (Miliolite chalk). 



The greater number of Foraminifera are marine, and move by 

 creeping on the bottom of the sea, but Globigerina and Orbulina have 

 been met with on the surface. The bottom of the sea at very consider- 

 able depths is also covered with a rich abundance of forms, especially 

 with Globigerina, the remains of the shells of which give rise to an 

 enduring deposit. 



1. Sub-order: Lobosa (Amocbiformes). Amoeba-like fresh -water 

 Rhizopoda, usually with pulsating vacuole, sometimes naked, some- 

 times with a single-chambered firm shell. The sarcode body consists 

 as a rule of a tougher exoplasm and a fluid granular endoplasm. 

 The pseudopodia are lobed or finger-shaped processes of considerable 



