E. PENARD OX SOME RHIZOPODS FROM SIERRA LEONE. 305 



ment of the shell itself, a kind of " devagination," the chitinous 

 envelope being in some way pushed out at certain points, in the 

 shape of a long, narrow tube. 



Sometimes the tube is pointed, simply closed at its extremity 

 {Fig. 8c), but much more commonly it retains its breadth to the 

 very end, or even expands, and is terminated by some foreign 

 particle taken from the mud ; these particles, always clear and 

 transparent, have the shape of a knife {d, e), or of an arrow- 

 head (/) ; sometimes a small diatom is recognisable, or the form is 

 very queer (g), and often the particles were small, shining coral- 

 like bodies {h, i), which were found also isolated in the mud, 

 and whose nature I could not decide upon. 



This species was very rare ; about a dozen specimens were 

 found, and only seven could be examined and studied with ease ; 

 all were alike, and the nature of the spines was always the same. 



Like the other Rhizopods of the collection, the shells were 

 mpty or filled by some decayed, yellowish remnant of the 

 plasma. 



Almost certainly we have here a Difflugia ; but should the 

 pseudopodia be filamentous, this species would belong to the 

 Filosa, and come very near the genus Pseudodijfflugia. 



Fragmentary as have been the results of these preliminary in- 

 vestigations, they allow of some general deductions, which go to 

 confirm the views of such observers as have had opportunities of 

 studying collections from all parts of the world. 



First, if most of the Rhizopods are common in many and 

 very distant countries, and with such characters as are sufficiently 

 alike to allow of recognising their specific identity, some differ- 

 ence, however, may always be expected from one station to 

 another ; difference in shape, in size, in structure ; mostly so 

 slight as not to be easily expressed by word or sketch, but some- 

 times sharp enough to point to a distinct variety. The Rhizopods, 

 in fact, like all other living beings, vary, according to the station, 

 and produce local forms, which are preserved in the locality. 



Secondly, if all the recent contributions to the study of these 

 organisms have confirmed the "cosmopolite" theory of their 

 distribution, we must yet come to an understanding as to the 

 meaning of the word. They are cosmopolitan in so far as, 

 sufficiently favourable conditions being given for a prosperous 



