8 4 



THE LOS OS A 



It is difficult to determine at present the true nature of many 

 of the amoeboid cells found in the pus and other fluids of patho- 

 logical conditions, but the following are regarded as parasitic 

 organisms : Amoeba urogenitalis, Amoeba kartulisi, 

 Amoeba buccalis. 



Leydenia gemmipara is an amoeboid cell originally 

 found by Lieberkiihn in the ascites fluid of malignant 

 tumours. The endoplasm contains numerous fat 

 spherules, remnants of red and white corpuscles, and 

 numerous crystalline bodies. The most remarkable 

 feature of Leydenia, however, is the presence of a 

 definite contractile vacuole. Plastogamy frequently 

 occurs, and reproduction is effected by fission and 

 gemmation. There seems to be little doubt from 

 the researches of Schaudinn that Leydenia is an in- 

 dependent organism, but whether it should be placed 

 with tne LoDOsa or with the Myxomycetes is not 



clear. 



teria; c, at the an- 

 terior pole granules 

 are seen arranged in 

 the direction of the 

 protoplasmic cur- 



rents (After schu- 



Opm 

 URDER 



The body is protected by a shell or test, which 

 may be perforated by a hole the pylome or 

 widely open on one side like a cap. The test is not perforated by 

 the pseudopodia. 



The test of the Thecamoebida is composed of two sheaths 

 an inner sheath, which is in the form of a thin continuous layer ; 

 and an outer sheath, which is usually much thicker, and may be 

 strengthened by the secretion of definite hard plates or by the 

 adhesion of foreign materials of various kinds. The chemical 

 constitution of the test is difficult to determine with accuracy, but 

 it appears to consist of an organic matrix usually containing silica 

 in larger or smaller proportions. The inner sheath of the test 

 contains a small proportion or only traces of silica ; the plates and 

 prisms of the outer sheath, such as we find in Quadrula and its 

 allies, contain a much larger proportion of silica. The matrix 

 which cements the plates of Quadrula together, and which fastens 

 diatom shells, grains of sand, and other foreign bodies to the test of 

 Difflugia, is an organic substance which also contains a trace of 

 silica. In the plates of Quadrula irregularis calcium appears to 

 take the place of silicon. 



There is no evidence of the occurrence of chitin in the tests of 

 any Thecamoebida, but a substance allied to keratin may occur in 

 some cases (Awerinzew [1]). 



In the Cochliopodiidae the shell is thin and flexible. It is 

 usually marked by minute punctuations arranged in definite rows 

 or more irregularly distributed. When more highly magnified 



