162 ESSAY ON CLASSIFICATION 



tion of species, especially when they are considered isolatedly, the 

 form is described at full length. Is there not in this indiscriminate 

 use of the term of form a confusion of ideas, a want of precision 

 in the estimation of what ought to be called form and what might 

 be designated by another name? It seems to me to be the case. In the 

 first place, when form is considered as characteristic of Radiata or 

 Articulata or any other of the great types of the animal kingdom, 

 it is evident that it is not a definite outline and well-determined 

 figure which is meant, but that here the word form is used as synonym 

 for plan. Who, for instance, would describe the tubular body of 

 an Holothuria as characterized by a form similar to that of the 

 Euryale, or that of an Echinus as identical with that of an Asterias? 

 And who does not see that, as far as the form is concerned, Holo- 

 thuria resemble Worms much more than they resemble any other 

 Echinoderm, though as far as the plan of their structure is concerned 

 they are genuine Radiates and have nothing to do with the Articu- 

 lates? 



Again, a superficial glance at any and all the classes of the animal 

 kingdom is sufficient to show that each contains animals of the most 

 diversified forms. What can be more different than Bats and Whales, 

 Herons and Parrots, Frogs and Sirens, Eels and Turbots, Butterflies 

 and Bugs, Lobsters and Barnacles, Nautilus and Cuttlefishes, Slugs 

 and Conchs, Clams and compound Asidians, Pentacrinus and Spatan- 

 gus, Beroe and Physalia, Actinia and Gorgonia? And yet they belong 

 respectively to the same class, as they are coupled here: Bats and 

 Whales together, etc. It must be obvious then that form cannot be 

 a characteristic element of classes, if we would understand anything 

 definite under that name. 



But form has a definite meaning understood everywhere when 

 applied to well known animals. We speak, for instance, of the human 

 form; an allusion to the form of a horse or that of a bull conveys at 

 once a distinct idea; everybody would acknowledge the similarity of 

 form of the horse and ass and knows how to distinguish them by 

 their form from dogs or cats, or from seals and porpoises. In this 

 definite meaning form corresponds also to what we call figure when 

 speaking of men and women, and it is when taken in this sense that 

 I would now consider the value of forms as characteristic of different 

 animals. We have seen that form cannot be considered as a character 



