SPECIAL MORPHOLOGY. 143 



that Nature presents no system for our scientific considerations, but 

 simply individual beings, between which no middle form can be imagined, 

 since the character of individuality precludes the possibility of varia- 

 tions. It is we ourselves who introduce into the number of individual 

 beings an arrangement and classification into larger or smaller groups, 

 species, races, or families. On finding a greater degree of uniformity 

 among a certain number of individuals, we arrange these together, and 

 then proceed to seek for an expression by which to characterise this 

 group. And it is only when we have learnt to know all the individuals 

 perfectly according to all their characters, and have made ourselves 

 thoroughly acquainted with ea.ch character in all its relations, that 

 we are enabled to find an expression that shall fully mark and distin- 

 guish the individuals of the group from those in that immediately suc- 

 ceeding it. As long, however, as this perfect knowledge is nothing 

 more than a mere desideratum, we content ourselves for the time with 

 the choice of any character that may seem most applicable for the 

 purposes of classification, although it may not be perfectly correct, and 

 may not draw the line as clearly as should be. Thus there will present 

 themselves many individuals which the provisionally adopted character 

 will not aid us in defining, and such we term Transition forms. These 

 exist, therefore, only as the creations of our ignorance ; and it is merely 

 owing to our own inefficient knowledge that we are unable to define 

 clearly the different boundaries, the occurrence of these transitions 

 affording us a criterion by which to judge of the great deficiency of our 

 information regarding any one particular point, and thus stimulating us 

 to further and more exact observations. 



There still remains a third signification of the word transition for 

 us to notice. We have not as yet found any expression for the nature 

 of the plant in general, which might enable us in doubtful cases to de- 

 cide upon the vegetable or animal nature of an object. On passing 

 from one certain group of plants to another, we must have common 

 parts of both by which the two groups may be connected together 

 under one general conception of plants, that we may know with 

 certainty that we are not encroaching upon the department of animal 

 life. This occurs everywhere, where we combine two or more subor- 

 dinate groups within the sphere of a higher conception ; and here, con- 

 sequently, the links necessary to convince us that we are correctly 

 embracing the lower groups under the idea of a higher one must be re- 

 garded as transitions from one group to another, although in a totally 

 different sense from the one already alluded to. Instead of the term 

 transition, I shall in the latter signification use the words " intervening 

 stage," limiting the application of transition merely to those cases where 

 the line of demarcation cannot be sharply defined, owing to the deficiency 

 of our knowledge on the subject. 



SECTION I. 



THE ANGIOSPORJS. 



79. Plants develope either from a naked cell, or, in the case of 

 Lichens and Fungi, from an enclosed and double cell, into such 

 multifarious and indefinite forms that no general character can be 



