Metazoa Lumbricus. 233 



SECTION II. VERMES LUMBRICUS. 



One of the largest of the natural groups into which the 

 animal kingdom is divided is the Vermes ; and this group is 

 of special importance, not only on account of its size, but 

 also because it is amongst the forms included within it that 

 we must look for the type on which the majority of the 

 lower animals are built. Moreover there is good reason to 

 believe that even the higher animals are closely related 

 genealogically to the worm group, for they undoubtedly still 

 retain many vermian characteristics, if not in their adult 

 state, yet in the embryonic phases of their life-history. 



To illustrate the group of the Vermes, and at the same 

 time to obtain a basis for the correct understanding of the 

 morphology of the higher forms of animal life, we may take 

 the common earthworm. Although Lumbricus is perhaps not 

 a perfectly satisfactory type of vermian structure, yet that dis- 

 advantage is more than counterbalanced by the readiness 

 with which it can be obtained, and the ease with which the 

 principal features in its anatomy may be made out. 



Lumbricus terrestris is familiarly known to everyone as 

 the animal which burrows in soft, moist earth, appearing on the 

 surface during rainy weather and sinking far down as drought 

 comes on. Its habits and general physiology are also well 

 known after their admirable expression in Darwin's work on 

 The Formation of Vegetable Mould by the Action of Worms. 

 That the earthworm swallows large quantities of mould from 

 which it extracts the small quantity of food material it re- 

 quires (in the form of decaying vegetable matter), and that 

 it has the remarkable power of replacing lost parts of its 

 body, and recovering from very serious injury, and that 

 rapidly too, are facts very familiar to everyone who has 

 handled a spade. The general appearance of the animal 

 also, the long, tapering, many jointed body, without any dis- 

 tinction into head, neck, trunk, and appendages, the marked 

 yellow band present nearer one end at certain seasons of 



