197 



tion with these lowly creatures are also of great interest. The 

 chief works on the group are Leidy's Fresh-water Rhizopods of 

 North America, Penard's Faune Rhizopodique die Bassin du 

 Leman, and a recently issued first volume of a monograph 

 on the subject in the Ray Society's series by Mr. J. Cash, of 

 Manchester. Mr. Scourfield then said a few words on the nature 

 and classification of rhizopods, and called attention to some of 

 the chief types. Rhizopods (root-footed animals) are unicellular 

 organisms, for the most part of very simple structure, belonging 

 to the lowest of the four main divisions of the Protozoa. A black- 

 board diagram and a description of Amoeba as a typical form were 

 given. Some differences of opinion exist as to the use of the 

 word " Rhizopoda." Leidy includes all the forms of the lowest 

 division of the Protozoa ; but it is more usual now, perhaps, to 

 limit the term to those forms which have lobelike or filiform 

 pseudopodia, and so to exclude the Heliozoa (sun animalcules) 

 and the Radiolaria (Polycystinae, etc.). Taking the word in its 

 restricted sense, the Rhizopoda fall pretty naturally into three 

 groups, according to the nature of their pseudopodia, viz. : (1) 

 Lobosa: Amoeba, Difflngia, etc. (2)Filosa: Eugbjpha,Cyphoderia, 

 etc. (3) Reticulosa : Foraminifera. The lobose rhizopods are 

 characterised by their lobe-like pseudopodia, which may be blunt 

 or pointed, but never thread-like ; and they never anastomose, 

 but may branch a little. Pilose rhizopods are characterised by 

 thread-like pseudopods, which branch a good deal and occasionally 

 anastomose. In the Reticulosa the pseudopods are thread-like, 

 much-branched, and freely anastomose. As to the number of 

 fresh-water rhizopods, it may be interesting to note that Leidy, 

 in his great work, only admitted twenty-four genera and sixty 

 species, excluding Heliozoa. The number admitted by Penard 

 and of her recent authors is something like 250 species, belonging 

 to, perhaps, sixty genera. This great increase is not because 

 the rhizopod fauna of North America is less rich than that of 

 Europe, for the forms are practically cosmopolitan, but is partly 

 due to the fact that Leidy was rather conservative in the matter 

 of genera and species, and figured many forms under one name 

 which are now considered good species. There is no doubt, how- 

 ever, that the main increase is due to the employment of better 

 lenses and closer attention to details of structure, both of proto- 

 plasm and shell. In concluding his remarks, Mr. Scourfield said 



