69G 



SCIENCE 



[N. S. Vol. XXV. No. 644 



sufficiently attested by the choice of the 

 subject of this discussion. I feel myself 

 here on treacherous ground and will ven- 

 ture no prediction as to whither the new 

 subject of medical protozoology may lead 

 us. But evidently the bacteria must look 

 to their laurels with so formidable a com- 

 petitor in the field. It is within the bounds 

 of possibility that the discovery of the 

 causal relation between protozoa and dis- 

 ease may one day rank with the greatest of 

 those that general biology owes to the study 

 of these simple animals. 



Some General Principles in connection with 

 Protozoa as Factors in Disease: C. W. 

 Stiles. 



The speaker first directed attention to the 

 difficulties of classification and the necessity 

 for extensive academic work on protozool- 

 ogy independent of the subject of applied 

 protozoology. Because of incomplete knowl- 

 edge of the protozoa, we must expect to 

 meet with extensive differences of opinion 

 in reference to numerous species or alleged 

 species, for some years to come. These dif- 

 ferences in interpretation are at present 

 inevitable and should be accepted as having 

 a right to existence ; they do not necessarily 

 indicate any special prejudice or unreason- 

 ableness on the part of contending authors. 

 Zoologists are at present not in a position 

 to concisely define the protozoa as a sys- 

 tematic unit, nor can they yet define sharp- 

 ly the different groups from one another. 

 We miist, therefore, have patience at pres- 

 ent and receive with open minds, al- 

 though with some reserve, many interpreta- 

 tions that are published. He referred to 

 the two biologic rules he had enunciated in 

 1901, to the effect that diseases which are 

 conveyed mechanically by arthropods (as 

 facultative carriers) may be due to either 

 plant or to ani nal parasites, but chiefly to 

 the former, while diseases which are con- 

 veyed biologically by arthropods (as oblig- 



atory carriers) are, so far as known, due 

 to animal parasites. In discussing the re- 

 lation of Rocky Mountain fever, African 

 tick fever and chicken spirillosis, to these 

 same rules, he held that we must await 

 further study in the case of Rocky Moun- 

 tain spotted fever, while in the case of tick 

 fever and chicken spirillosis it has not yet 

 been proved that the ticks are biological 

 (obligatory) carriers. In chicken spiril- 

 losis the disease has, according to litera- 

 ture, been conveyed through feeding the 

 feces of a sick animal to a well animal, 

 hence in nature, this disease does not seem 

 biologically dependent on the ticks. As 

 for African fever, there are certain indica- 

 tions, though as yet no proof, that this 

 can be conveyed as a wound disease. 



Passing to yellow fever, the speaker 

 thought that despite certain opinions to 

 the contrary, the present indications re- 

 main in favor of a protozoal rather than a 

 protophytic origin. 



The Protozoan Species: Gary N. Calkins. 



Formerly it was the custom to base pro- 

 tozoan species on the structure of the single 

 cell. This made it very easy to make new 

 species, for any novice with a microscope 

 might see known organisms new to him and 

 describe them as new species thus burden- 

 ing the literature with names and pseu- 

 donyms. On this former basis there were 

 so few points of structure to base species 

 upon that they were difficult to accurately 

 define. 



A species in zoology is an abstract con- 

 ception of a group of animals based upon 

 similarity in structure, habits and mode of 

 life and power of reproducing amongst 

 themselves offspring identical with them- 

 selves. 



In the single individual of a species we 

 usually recognize more or less clearly de- 

 fined variations in vitality and sequence of 

 changes which we designate as youth, adol- 



