THE SUCTORIAL FORM. 255 



stances it is not, in fact, apparent. All animals be- 

 longing to tliis type are shy, and evince little or no 

 propensity to become domesticated. They are without 

 offensive protection ; but nature, as if to screen them 

 from their enemies, has endowed them with great 

 caution, uncommon vitality, and in many cases has 

 protected them either with a hard skin or a coating of 

 bony armour, which entirely envelopes their body, and 

 repels all injui-y. When compared to the pre-eminent 

 examples of their respective circles, the suctorial type may 

 be viewed as the most imperfect ; that is, the most simple 

 in its organisation, and the most dissimilar from all others. 

 (315.) Let us now see in what manner this type is 

 developed in the more comprehensive divisions of the 

 animal world. The polypes and the animalcula {Acrita) 

 are the smallest of aU living beings. Thousands are in- 

 visible to the naked eye ; and these, even when viewed 

 under the microscope, appear but as grains of sand, 

 mere particles of matter, so simple in their structure as 

 often to be without limbs, and only recognised as animals 

 from being endowed with voluntary motion. In what 

 manner they are nourished, — whether by absorbing the 

 fluid in which they live, or by sucking the juices of 

 other beings still more imperceptible than themselves, 

 — is immaterial to our present purpose, as both are 

 obvious modifications of the suctorial process. In 

 the vertebrated circle, comprehending the most perfect 

 of all animals, this type of imperfection is confined 

 to a very small number. Of these the siren of Lin- 

 naeus is probably the type : it is, perhaps, the most 

 defenceless of animals ; living, Uke the worms, in the 

 muddy bottoms of ponds, destitute almost of eyes, with- 

 out teeth, and whose feet are so inefficient as to appear 

 like unserviceable appendages. In the great division of 

 annulose animals we have all these types represented by 

 the intestinal worms ; whose structure, indeed, is so im- 

 perfectly jointed, that in some of the modern systems 

 we find them referred to the Acrita or polypes : they are 

 nevertheless truly annulose, and give us the most perfect 



