328 On the Variations of certain Crustacea. 



Central Departments only."* Our conrmon bramble, Rubus 

 fruticosus, is a parallel example. By some botanists it may 

 still be, as it used to be, considered as one very variable 

 species ; by otters it is divided into a multitude of distinct 

 species : that these are " good" species, according to any 

 possible morphological or physiological test, I cannot believe, 

 though their distinction by specific names may be very con- 

 venient to the botanist. But suppose a few links in different 

 parts of this chain to be lost, then there would be no question 

 as to the " goodness" of the several species. And this con- 

 tinuity is equally apparent in the animal kingdom. Dr. Car- 

 penter's conclusions with respect to the Foramimfera are that 

 their range of variation is so great as to include, not merely 

 the differential characters which have been accounted specific, 

 but also those upon which the greater part of the genera, or 

 even in some instances the orders^ have been founded ; that the 

 ordinary notion of species as assemblages of individuals 

 marked out from each other by definite characters that have 

 been genetically transmitted from original prototypes similarly 

 distinguished, is quite inapplicable to this group ; since even 

 if the limits of such assemblages were extended so as to in- 

 clude what elsewhere would be accounted genera, they would 

 still be found so closely connected by gradational links, that 

 definite lines could not be drawn between them : that any 

 arrangement of genera and species which may for convenience 

 be adopted, must be regarded merely as assemblages of forms 

 characterized by the nature and degree of modification of the 

 original type, which they may have respectively acquired in 

 the course of genetic descent from a common ancestry ; that 

 even as to the family types it may fairly be questioned whether 

 analogical evidence does not rather favour the idea of their 

 derivation from a common original than that of their primitive 

 distinctness, t 



My object, however, in the present paper, is to give a brief 

 account of some recent researches of two German naturalists, 

 Dr. Muller, and more particularly Dr. Claus, the Professor of 

 Natural History at Marburg. The work of Dr. Fritz Muller, 

 Fur Darwin, I know only by some extracts given about a year 

 ago in the Annals and Magazine of Natural History. These 

 are especially interesting, inasmuch as the author conducted 

 his investigations on a deductive, instead of on the usual 

 inductive plan ; that is to say, instead of in the first instance 

 ascertaining a number of facts, and then looking for some 

 general explanation of them, he, to begin with, set before him- 

 self Darwin's theory of descent, and said, " If this theory be 



J. G. Baker, Review of the British Hoses. 

 t Dr. Carpenter, quoted by Mr. Grove, Address to British Association. 



