440 



SCIENCE 



[Vol. LVI, No. 1451 



a 3x1 glass slide. Before this has a chance to 

 diry drop it face downward into a dish con- 

 taining Sehaudinn's fixing solution. This is 

 made up of a saturated solution of mercuric 

 chloride in distilled water, 200 e.c; 95 per 

 cent, alcohol, 100 c.e. ; and gflaeial acetic acid, 

 15 c.c. Leave in this solution for about ten 

 minutes. The slide should then be treated by 

 the well-known iron-hcemotoxylin method (70 

 per cent, alcohol plus iodin, 30 minutes to 24 

 hours; water, a few minutes; four per cent, 

 aqueous solution of iron alum, 1 to 4 hours; 

 rinse in water; 0.5 per cent, aqueous solution 

 of hsemotoxylin, 4 to 24 liours; rinse in water; 

 differentiate in two per cent, iron alum; wash 

 thoroughly; dehydrate; mount). 



Giardia agilis inhabits the anterior portion 

 of the intestine. First observed by Kunstler 

 in 1882, it has recently been studied in detail 

 (Hegnea-, 1922). When alive it looks like a 

 minute, slender tadpole and undergoes ex- 

 tremely rapid wriggling movements which no 

 dou!bt suggested its specific name. When fixed 

 and stained as suggested above it exhibits 

 bilateral symmetry, with two nuclei, fom- pairs 

 of flagella with intracytoplasmic portions, a 

 pair of axostyles, and one or several parabasal 

 bodies. Another species of this genus, G-iardia 

 lamblia, occurs in about 12 per cent, of human 

 ■beings (Hegner and Payne, 1921). This spe- 

 cies, which has been carefully studied and 

 described by Simon (1921, 1922), is considered 

 by some to be responsible for serious intestinal 

 disturbances, but may be present in apparently 

 healthy persons. 



Trichomonas augusta is confined principally 

 to the rectum, although it occurs occasionally 

 in the intestine of the tadpole. This flagellate 

 may be recognized by its jerky movement. 

 When the living animal is examined with high 

 magnification its active undulating membrane, 

 along the outer edge of which is fastened a 

 flagellum, ■ can be seen ; waves of motion start 

 at the anterior end and pass posteriorly to the 

 end of the body. Such an undulating mem- 

 brane is characteristic of certain parasitic pro- 

 tozoa. The pointed extension of the rod-like 

 axostyle may also be seen protruding from the 

 posterior end. When fixed and stained a single 

 nucleus, three anterior tlagella, the undula;ting 



membrane, axostyle and mouth are clearly re- 

 vealed. A species of Trichomonas, T. hominis, 

 that occurs in man is similar in appeai-ance to 

 that in the tadpole ibut does not stain well and 

 hence its structure is difficult to determine. 

 Triehomonads that have ibeen recorded from 

 man are T. hominis, in the intestine ; I. vagina- 

 lis, in the vagina ; and T. buccalis, in the mouth. 

 The intestinal form has been found in about 

 three per cent, of the human beings examined. 



Hexamitus intestinalis is a very minute spe- 

 cies with two nuclei, and four anterior and two 

 posterior flagella. It is an active swimmer and 

 moves rapidly across the microscopic field. It 

 differs from Trichomonas in the albsence of a 

 mouth and probably takes in its food through 

 the sui'face of the body. No species of this 

 genus are known from man. 



Nyctotherus cordiformis is a very large 

 ciliate that is often found in the rectum of 

 tadpoles. It appears to be a scavenger and 

 resemljles Paramecium in structure and in its 

 primary life processes. A species of this 

 genus, N. faba, has ibeen recorded from man. 



Opalina ranariim is also a large ciliate that 

 is a frequent inhabitant of the rectum of tad- 

 poles. This and other species of Opalina that 

 also may be encountered in this habitat are 

 especially interesting because of their poly- 

 nuclear condition and absence of an oral aper- 

 ture, food being albsorbed tShrough the body 

 wall. The vai-iations in nuclear number and 

 structure in various members of the Opalinidfs 

 are of particular interest (Metcalf, 1914). The 

 value of these protozoa with respect to prob- 

 lems of geographical disti'ibution has been em- 

 phasized by Metcalf (in press). 



Balantidium entozoon is an inhabitant of the 

 rectum of certain frogs. It has not been found 

 by the writer in tadpoles, but probably occurs 

 in them in certain localities. Its mouth is situ- 

 ated near the anterior end instead of forming 

 a large conspicuous crescent near the center of 

 the body as in Nyctotherus. A human species 

 of Balantidium, B. coli, although not very 

 common, is sometimes very pathogenic, causing 

 intestinal ulcers and frequently bringing about 

 the death of the host. > 



Endamaba ranarum is a species that is often 

 abundant in tadpoles. It is of particular in- 



