16 



not, they show mutual affinities often of the closest kind. It is 

 quite impossible to string them altogether in one straight line 

 reaching from the lowest to the highest as was formerly supposed : 

 they rather fonn a complicated network, radiating and branching 

 out in all directions, each species showing relationships more or 

 less striking to a multitude of others. They are all subject to 

 the same general laws of organisation ; and there are certain first 

 principles of life and structure, as well as of classification, which 

 apply to all alike, and which must be understood by him who 

 desires to investigate their natural history with any hope of 

 success. 



A general knowledge of science in all its branches is advan- 

 tageous to the student in another way. It is calculated to remove 

 that narrow-mindedness which sometimes attaches to those who 

 confine themselves to one department of it exclusively. The 

 physicist has occasional!}' looked down upon the naturalist as 

 devoting his attention to objects of inferior consideration to those 

 which he himself studies. Even among naturalists, those who 

 have chosen for themselves the study of the higher animals have 

 sometimes underrated the labours of the conchologist and entomo- 

 logist, and yet more the researches of others, who, perhaps, give 

 all their time and attention to the investigation of the minute 

 infusoria, or of those most repulsive of all animated forms — the 

 entozoa. 



It may be true that, at the present day, feelings such as these 

 are not entertained so much as formerly, and that men of 

 whatever rank who devote themselves to science at all, are 

 considered but as fellow-workers in a common field. But still 

 there is a narrow-mindedness, which, without reference to others, 

 may hinder us in our own studies, when too confined, in respect 

 of the method in which we conduct them and the judgments Ave 

 form. Xaturalists, especially, who are only acquainted with one 

 particular class of animals, have been frequently led to entertain 

 erroneous estimates of the importance of certain organs and 



