MICRO-ORGANISMS 33 



thermore, when the spores germinate, they form germ tubes rather 

 than motile spores. If one now turns to a general treatment of all the 

 fungi, such as the key by Martin (22), one sees that the fungus must 

 belong to the class Phycomycetes, and that because many spores are 

 borne in sporangia, it belongs to the order Mucorales. Further study 

 of the culture indicates that in the original isolation plate zygospores 

 are present, and after isolating several individuals, zygospores are 

 formed when the proper strains are put together. It is obvious now 

 that the material under study belongs in the family Mucoraceae. 



In order to proceed further, one must now refer to one or more 

 monographic treatments on this family to get detailed descriptions of 

 the genera and the species. Often one may be sufficiently familiar 

 with the organism to tell at a glance that it belongs in a certain class, 

 order, family, and even genus, so that he can start immediately with a 

 detailed treatment. Assuming that a complete treatment of the genus 

 is available, such as RMzoyus, one must then determine from this 

 treatment the conditions required to duplicate that of the monograph. 

 For instance, one finds that among the first characteristics to be de- 

 termined is whether the fungus will grow at 37° C. and whether the 

 spores are marked in a peculiar fashion when grown on malt agar. 

 The same temperature, media, and other conditions should be used 

 regardless of whether they are best for growth or not. Of course, 

 if at a later time one may want to monograph a particular genus, then 

 he can introduce various other conditions. But, for identification 

 only, one should always try to compare the organism under as nearly 

 as possible the same set of conditions as those in the monographic 

 treatment. 



Next, step by step each characteristic should be checked and com- 

 pared to those found in the descriptions. If the identification is still 

 in doubt, an attempt then should be made to obtain a type culture 

 or a type specimen in the form of dried material, or a slide, to make 

 an actual comparison. Even when this type material is obtained, es- 

 pecially a culture, it should be examined critically and compared with 

 the published description. This check should preferably be made 

 with the original published description prepared when the organism 

 was first described, provided it is recent. Many species descriptions 

 published 75 or 100 years ago are so incomplete that they are of little 

 use, except to the specialist. Some individuals assume that if the 

 type culture is obtained, it is above question. However, sometimes 

 this type culture has degenerated, so it is no longer typical of the 

 natural occurring strains, or it has been completely replaced by a 

 contaminant. It is, therefore, always necessary to check a reference 

 strain against the published description. 



After a comparative study has been made, if one is still uncertain 

 as to the identity of the organism, he should then send it to an expert 

 on the group for study. The specialist has many other duties and 

 should not be burdened with frequent and repeated identifications. 

 The specialist should be supplied with all the pertinent information 

 needed for the identification. It is also understood that he may, if 

 he chooses, describe the organism as a new species or use it in his 

 studies. It is not ethical to send the same culture to two individuals 

 for identification unless both are told that you have done so. 



