IOWA ACADEMY OF SCIENCES. 73 



respects they are essentially alike. Prof. Osborn further calls my attention t) the 

 fact that in gall insects the character of the gall produced by the insect is of great 

 importance in separating species. 



I may be permitted in this connection to briefly quote from several prominent 

 writers on this question. Trealease-* summarized the chf'racters as follows: 1. 

 Morphological characters, mode of growth in which cultures show full range of 

 variability of each species, behavior of cells to staining fluids, motion of the cells. 

 2. Physiological characters, production of pigment, specific fermentation and 

 liquefaction of gelatin are apparently reliable. 3. Pathogenic characters for the 

 most part are unreliable to render species which depend at all upon them above 

 suspicion, though they may offer valuable collateral evidence. Any physiological 

 characters therefore to be useful in the delimitation of species of bacteria, must be 

 reasonably constant as well as pronounced. The fact is with our present. means of 

 cultivating bacteria, strictly parasitic, like the Spirochceta of relapsing fever; that it 

 grows with great difficulty in artificial cultures, like the Micrococcus of gonorrhoea, 

 that it dies after a short time when cultivated, unless re-innoculated like the swine 

 plague bacillus of the Germans and our Department of Agriculture all the pecular- 

 ities have at least a suggestive value." Fraenkel-" writes: "Were the micro, 

 scopical examination of the bacteria as they occur in their natural state, the only 

 means at our disposal for studying them, our knowledge of bacteriology would 

 never get beyond the experimental stage of certain very narrow limits." H. Marshall 

 Ward'" in an admirable article says that before new species are described the fol- 

 lowing points should be clearly made out: 1st. Habitat, air, soil, milk, etc. 2d. 

 Nutrient medium agar, gelatin, potatoes, broth, saccharine liquids, etc. 3d. 

 Gaseous environment, aerobic, anaerobic, whether carbon dioxide, nitrogen or 

 hydrogen aff"ect the growth. 4th. Temperature-optimum is the most important 

 though maximum and minimum should also be recorded. 5th. Morphology and 

 life-history, shape, size, mode of union, presence of sheaths and capsules, spores, 

 endospores and arthrospores, cilia, involution forms, etc. 6th. Special behavior. 

 Does the germ peptonize and liquefy gelatin? 7th. What is the shape and course 

 of the area? What is the shape of the colony? 8th. Pathogenic properties. But 

 before we can do a great deal in this line some general code should be adopted. 



From these observations it will be seen that it is not an easy matter to recog- 

 nize species; partial descriptions must be entirely ignored. I will admit with H. 

 Marshall Ward that some general standard should be set up. But it would seem 

 to me that we should soon begin to do something more on the biological charac- 

 ters of many species. Many of these points in our species are still in a somewhat 

 uncertain state. They have, in fact, not been determined. 



Much bacteriological work can be done with little equipment, but the systematic 

 portion of this work can not be done without the literature at hand. To work out 

 our bacteriological flora is needed, but it may be a long time before this work is 

 accomplished. What is needed is a thorough scrutinizing of species to determine 

 how many of these are synonyms. Marshall Ward^' has attempted this for a good 

 many of the species occurring in water, and he has what appears to me, placed 

 together some species which are distinct. Marshall W'-^rd is however, a most 

 careful investigator, who discriminates with great care. This part of the work can 



2«The Weekly Medical Review, Vol. XIX, March 23, 1889, p. 315. St. Louis 

 2»Text Book of Baeterioloiiy. 



30Oa the Characters, or Marks, eL\ployed forclassiflying the Schizomycetes, Annals 

 of Botany. Vol. VI, No. XXI, Apill, 1392, pp. 103-144. 

 siPhllosophical Transactions, 1892 or 1893. 



