'73 



of which the intestine passes. This latter has first a glandular greenish yellow layer, 

 which above is laterally produced into the lobes of the liver, and which are separated by 

 the dorsal canal of the water vascular system. Inside the greenish yellow layer come suc- 

 cessively a longitudinal and circular layer of muscles, and then inside these another glandu- 

 lar layer covered internally by thin cells. This has brought us to the cavity of the intestine, 

 which is simply a tube running from the mouth to the end of the body, but it is peculiarly 

 formed, having almost the appearance of a tube within a tube. This arises from the fact 

 that the tube of the intestine is much larger than the space it has to occupy. The only 

 way then it can be contained is by having the upper wall folded into a sort of loop inside 

 the canal. This is hard to explain, but can be easily understood if the two ends of a 

 piece of string about a yard long are tied together so as to make a large ring. Now let 

 anyone take hold of this ring with the hands about a foot apart, and then bring their 

 hands together so as almost to meet, when a small ring will drop down inside the larger 

 ring. This will give just the shape of a worm's intestine. This curious fold is called the 

 typhlosole. I have mentioned that between the two lobes of the liver and directly beneath 

 the middle of the back and above the intestine is the dorsal canal of the water vascular 

 system. Just beneath the intestine in one section will be seen four circular marks, ©®o; 

 the top and bottom ones of these are the canals of the water vascular system, and the 

 pair in the middle are the double chained nervous cord. 



The simple digestive system or intestinal canal, which is in the form of a more or 

 less muscular tube, is divided into a strong pharynx, which is pushed forward when the 

 animal is forcing its head like an awl between the particles of loose soil, or drawn back 

 either when it is used as a sucker to draw in food or when the mouth is used to draw 

 heavy or smooth objects towards the burrow. This pharynx is analogous to the pro- 

 trusible proboscis which is found among some Annelids (Eunicidae, Lycidicse, Nereidse). 

 The pharynx leads into the oesophagus, which bears on each side of the lower part three 

 large calciferous glands. In most species there is a crop in front of the gizzard. This 

 latter organ is surrounded by a double set of very powerful muscles. Grains of sand and 

 small stones from one-twentieth to a little more than one-tenth of an inch in diameter 

 may be found in the gizzard and intestines, and are supposed to serve like millstones to 

 triturate the food. The gizzard opens into the intestine. The calciferous glands are 

 very remarkable, for nothing like them is known in any other animal. Their use is 

 largely a matter of speculation, and Darwin in his recent work, *'The Formation of 

 Vegetable Mould through the action of Earthworms," says of them; "Almost as many 

 theories have been advanced on their use as there have been observers." The author of 

 the above-mentioned work has, in it, collected together and himself verified almost all 

 the facts which have been recorded concerning earthworms by previous observers. The 

 results of his studies, too, are most reliable, from his character of scientific candour. He 

 never neglected, in the discussion of any subject, to examine all sides of the question, and 

 to weigh carefully all opinions, whether adverse to his own views or not. This work is 

 the result of continued and persevering study for a space of nearly fifty years. I shall 

 to a large extent use his words in this history of the work worms perform. 



With regard to the calciferous glands, he thinks that they serve primarily as organs 

 of excretion ; and secondarily as aids to digestion. The food of worms consists of organic 

 matter in a state of decay. This they either obtain from the soil, which they swallow in 

 large quantities, both when they are excavating their burrows, but also for food, or else 

 direct from the leaves of plants, which they drag into their holes. 



He says, p. 49, " Worms consume many fallen leaves ; and it is known that lime 

 goes on accumulating in leaves until .they drop off the parent plant, instead of being 

 reabsorbed into the stem or roots, like various other organic and inorganic substances. 

 The ashes of a leaf of an acacia have been known to contain as much as seventy -two per 

 cent, of lime, worms therefore would be liable to become charged with this earth unless 

 there were some special means for its excretion ; and the calciferous glands are well 

 adapted for this purpose." When these glands have excreted, a certain amount of lime it is 

 expelled into the alimentary canal j from the four posterior glands in the shape of minute 

 cells, and from the two anterior in the shape of large concretions. It is supposed that 

 the carbonate of lime so formed aids materially the process of digestion by neutralizing 



