A MONOGRAPH OF THE MYCETOZOA. 119 



figures and plates, make the work exceedingly valuable for the 

 student. 



The arrangement adopted is that of Eostafinski. Two things 

 are to be attained by any classification of natural objects : one is 

 convenience, the other is the expression of ascertained facts of 

 relationship. Now, while it is true that no scheme of classification 

 can express all the facts of relationship, and that convenience 

 therefore seems to win greater consideration, still the best form of 

 arrangement will with convenience combine the largest expression 

 of truth. Eostafinski's arrangement is convenient, but that, even 

 as here modified, it conveys the best impression of the real relation- 

 ship of the various families and genera will, we believe, be freely 

 questioned. Of course, adopting Eostafinski's general scheme, 

 Mr. Lister prefers the title Mycetozoa to the more familiar Myxo- 

 mycetes. If it be objected to Wallroth's name, Myyiomycctes, that 

 the organisms are not fungi, it may be with equal force urged that 

 they are not animals, and so the term Mycetozoa is equally at 

 fault. If we change current usage at all, we must adopt Fries's 

 designation, Myxogastres, which is non-committal as to etymology, 

 and has priority. 



When we examine further, and consider the author's disposition 

 of families and genera, we find him very conservative. He retains, 

 for instance, Comatricha as distinct from Steinonitis, and Henri' 

 arcyria, hereafter to be known as Hemitiickia, as distinct from 

 Arcyria. On the other hand, Tilmadoche is merged with Fhysarum, 

 and Ophiotheca with Perichana. In all this Mr. Lister will have 

 the support of students generally. In the matter of specific 

 determinations occur, as was to be expected, the greatest number 

 of innovations. Not only do many old friends, on account of some 

 prior christening, appear here under unfamiliar names, but a great 

 many lose identity altogether, and are mentioned as synonyms only, 

 or varieties of species thought to possess more definite and abiding 

 characters. No doubt in many cases this is excellent. Of making 

 many species there is no end. Nevertheless our zeal in this regard 

 may carry us too far. Whenever a form possesses definite characters 

 which are uniformly present, it should constitute a species. The 

 number of such characters may vary, does vary in different cases. 

 When too many divergent forms, even with diflerences comparatively 

 slight, are crowded under one description, the tendency is not to 

 clearness, but to confusion. A student will be led to regard any 

 approximate resemblance as sufficient for determination. Further- 

 more, when it comes to grouping related forms under one or other 

 established specific name, different authors are certain to differ as 

 to how the groups shall rise, how be constituted. Take, for instance, 

 Physarum compressiim A. & S. The Physarums are no doubt a 

 difficult set ; but is there anything to be gained by grouping together 

 four or five forms which are confessedly so distinct as to constitute 

 varieties, and which difi'er so far as to require a separate description 

 for each '? Again, the amount of variation necessary to establish a 

 species is not, cannot be a constant quantity to be measured alike 

 for the species of all genera. A slight difierence, it would appear, 



