284 ANAER0BI0SI8 AND ENDOPARA^ITWM 



ganizatiou of the animals : the development of the pellicle 

 into a kind of skeleton, the prevalence of a deeply sculp- 

 tured pellicle, the torsion of the body which occurs in 

 many forms, the development of very long cilia and of 

 tufts of flagella and finally the accumulation of large re- 

 serves of polysaccharides. Lauterborn is of the opinion 

 that these similarities may not be without significance 

 for the question of the origin of these parasites ; from no 

 other habitat is the transition in external conditions less 

 abrupt than from the sapropelic to the intestinal. Al- 

 sterberg's main objections (c/. above) to a derivation of 

 intestinal worms from mud-dwelling ancestors are not 

 valid in this instance. The sapropelic ciliates are ob- 

 viously well fitted to assimilate food in the absence of 

 oxygen; indeed, as has been shown before, they are even 

 harmed by oxygen. Since some of them seem capable 

 of utilizing cellulose, their environment is also quite rich 

 in food material. The same holds true even for forms 

 that cannot do so; pure bacteria feeders or scavengers 

 will find a rich source of food in the bacteria develop- 

 ing on the decaying organic matter that is characteristic 

 of a typical sapropelic mud. Of course, one cannot think 

 of a direct connection between the present-day sapropelic 

 protozoa and the rumen- or termite-protozoa. They 

 are all highly specialized forms and, to the writer 's 

 knowledge, not even common genera occur. They, most 

 likely, have a long history behind them. As to the gen- 

 eral similarities in organization, they may just be an ex- 

 pression of convergent development, but the derivation 

 of the three faunas from the same ancestral mud-dwell- 

 ers still remains a possibility. 



