205 



ANIMALCULES. 



ANNELIDA. 



Amongst the most successful cultivators of these sciences is Professor 

 Owen, who, in his courses of lectures as Hunterian professor at the 

 Royal College of Surgeons, and in his published works, has done much 

 for their advancement. In his application of comparative anatomy 

 to the explanation of the structure of extinct animals, he has been 

 scarcely less successful than Cuvier, as his works on ' Fossil Mammals,' 

 ' Birds and Reptiles of Great Britain,' and his papers on the ' Dinornis," 

 the 'Mylodon,' and 'Glyptodon' testify. He has also successfully 

 applied the principles of the transcendental anatomists to the eluci- 

 dation of the structure of the vertebrate skeleton in his work on the 

 ' Nomolopes of the Skeleton of the Vertebrata.' Added to his great 

 powers of generalisation, he possesses great industry, and his lecture 

 on ' Comparative Anatomy,' his ' Odontography,' and multitudinous 

 papers, bear witness that there is scarcely any department of our 

 knowledge of tho animal kingdom, that does not bear the marks of 

 his genius. Dr. J. G. Gray, as head of the Zoological department of 

 the British Museum, has contributed largely to our knowledge of 

 animal forms. His papers in the Magazines and Transactions of scien- 

 tific societies amount to nearly 500 separate contributions. The 

 works of Gould have contributed greatly to our recent knowledge 

 of birds. Edward Forbes has most industriously laboured at the 

 Marine Zoology of the British Islands, and his works on the ' Star- 

 Fishes ;' the ' Naked-Eyed Jelly-Fishes,' and the 'Mollusca of Great 

 Britain," have contributed greatly to extend our knowledge of these 

 families ; whilst his researches on the distribution of marine animals 

 in depth, have given a new direction to geological inquiries. To 

 Professor Bell, Mr. Yarrell, Dr. Johnstone, and Dr. Baird, zoology 

 is greatly indebted for their works on the ' Mammalia,' ' Birds,' 

 ' Reptiles,' ' Fishes,' and ' Crustacea, ' of the British Islands. The 

 natural history catalogues of the British Museum contain descriptions 

 of many new species, especially that devoted to the various forms 

 of Zoophytes, and which has been undertaken by Mr. Rusk. One of the 

 greatest contributions ever made to our knowledge of shells, has been 

 the collection made by Mr. Cuming, who is now resident in London. 

 We ought also to mention the labours of Mr. Dauvin on the family 

 of Cirripedes, the Sea-Acorns, and Barnacles. The voyages of Belcher, 

 Stanley, Kellert, Ross, Fitzroy, and others have added greatly to the 

 number of animal forms. 



The ' Marine Vivarium,' recently formed at the Zoological Gardens, 

 Regent's Park, London, will afford great assistance in the study of the 

 organisation and habits of fishes and of marine invertebrate animals. 

 Here may be seen, through the walls of glass tanks, in miniature 

 oceans of sea-water, the daily life of lobsters, crabs, and shrimps 

 (Crustacea), of sea-urchins (Echinidce), of star-fishes (Asterias, Stel- 

 leridiani), of the beautiful sea-anemones, or animal-flowers (A ctinidte), 

 of sea-mice and sea-eggs (Annelida), of barnacles and sea-acorns 

 'la), and many others. 



(Those who would study the subject of the general arrangement of 

 the Animal Kingdom, are referred to the following works : Cuvier, 

 Serfite Animal; Owen, Lecture* on Comparative Anatomy; Grant 

 ' .'"in Curative Anatomy ; Patterson, Zooloyy for Schools ; Rymer Jones, 

 * of the A nimal Kingdom ; Milne-Edwards, Element de Zoologie ; 

 Carpenter, Principles of Physiology.) 



ANIMA'LCULES, in Zoology, is the name which has been applied 

 to small animals of various classes, which cannot be distinctly seen 

 without the use of a microscope, as the minute radiate animal of the 

 coral, the worms found in paste, vinegar, and vegetable infusions, or 

 the smaller Crustacea found in pools, as the Monoculi. [INFUSORIA ; 



POLYGASTRICA ; ROTIFERA.] 



AXKERITE, a mineral found at Salzburg, in the Alps, and other 

 parts of the world, consisting of the carbonates of lime, magnesia, iron, 

 and manganese in the following proportions : Carbonate of Lime, 51 "1 1 ; 

 Carbonate of Magnesia, 25'7 ; Carbonate of Iron, 20'0 ; Carbonate of 

 Manganese, 3'0. It occurs crystallised, and its primary form is a 

 rhomboid. The cleavage is parallel to the primary planes. The 

 colour is white or yellow, or brownish. 



AN N'E'LIDA (Cuvier), an extensive division or class of animals, 

 established by modern naturalists partly at the expense of Linnaeus' 

 heterogeneous class of Worms ( Vermes). It was Baron Cuvier who 

 in 1802 first proposed to distinguish tlie Annelida as a class, chiefly 

 on account of their blood being of a red colour, as in the leech, and 

 circulating by means of a double system of complicated blood-vessels. 



The name is derived from the Latin word annulut, a ring, because 

 the animals arranged under this division always have their bodies 

 formed of a great number of small rings, as in the earth-worm. Their 

 external covering, or skin, is soft and pliable ; and their bodies, having 

 no bony skeleton, are soft, and in general more or less of a cylindrical 

 form. 



The Annelida are for the most part oviparous, but the leeches and 

 earth-worms deposit what are termed capsules, or membranous 

 cocoons, containing many embryo young. 



There is little variety in their mode of life. Some live in fresh and 

 others in salt water ; and others, like the Hair- Worm (Gordius), are 

 :iiii|tiiihi<nn. Some species construct tubes in the interior of stones, 

 or in shells, which they perforate, or in madrepores. Some species 

 again form calcareous cases, or cement around them various foreign 

 substances, particularly sand. The sedentary species are timid, and 

 when taken from tht-ir retreats can neither escape nor defend them- 



selves. The Errantia, on the other hand, are frequently very nimble, 

 and can defend themselves well by means of their bristles. 



Although manifestly a low group of the Articulate siib-kingdom to 

 which they belong, Cuvier was so led away by the importance he 

 attached to their possessing red blood, that in his latest edition of the 

 ' Regne Animal ' he placed them at the head of the Articulate series, 

 above the Crustaceas, the Arachnidas, and the Insects. A very cursory 

 examination would suffice to show that the Annelida represent the 

 caterpillar or larval condition of the insects, and could hardly be 

 regarded as higher in organisation than the perfected insect. 



The body of the Aunelide is long and soft, and divided into a 

 number of segments which agree in having the same form and nearly 

 the same size throughout. In the lower forms, the first segment is 

 not modified sufficiently to demand the name of a head ; but in the 

 higher forms it assumes the character of a head, and has organs 

 adapted to the performance of cephalic functions. 



In the most imperfect Annelides the organs of motion are suctorial 

 disks such as are seen in the Trematode worms amongst the Entozoa. 

 As we ascend, hairs or hooks project from the lateral segments, as in 

 the Earth- Worm. In others, bundles of hairs on each side take the 

 place of locomotive members, as in Aphrodita. These bristles or 

 bundles of hairs act as their weapons of attack and defence, and they 

 are generally sharp or barbed to assist in that office. 



The nervous system of the Annelides presents a great advance on 

 that of the class immediately below them, the White-Blooded Parasitic 

 Worms. It embraces a double central cord or chain of small ganglia 

 passing from one end of the body to the other. Most of the species 

 are provided with ocelei or fixed eyes, and the cephalic segment is 

 furnished with soft cylindrical tentacles which have been called 

 ' antennse.' These are undoubtedly organs of touch, but they differ 

 structurally from the antennae of insects in the absence of joints. The 

 mouth is seated 'at the lower surface of the head, and in some species 

 there is also a trunk or proboscis which the creature has the power 

 of pulling in at will, and lateral-curved horny jaws. The alimentary 

 c:tn;tl is generally straight ; in some species quite simple, in others 

 having lateral pouches. The anal orifice is situated above or at the 

 lower end of the body. The blood varies in its degree of redness, 

 being sometimes very pale, at other times of a greenish hue. It has 

 no visible corpuscles, molecules, or cells whatever. There - is no dis- 

 tinction into nervous and arterial. The circulating system is very 

 simple, consisting of a dorsal and ventral vessel with lateral branches 

 passing to the tegumentary system, the peritoneal and branchial 

 systems. In the dorsal trunk the blood flows from the tail towards 

 the head, and. in the ventral trunk from the head towards the tail. 



The respiratory system is in some of the Annelides adapted for 

 obtaining oxygen from the air, and in the rest through the medium 

 of water. The branchial organs or gills by which the blood is aerated 

 in the water are situated externally, and vary much in position. 



These are the general features in the anatomical structure of the 

 Annelides. They exhibit great variety in their passage from the 

 lowest to the highest forms. They are divided by Milne-Edwards, 

 who, after Cuvier, has given this family most attention, into four 

 orders : 



1. The Dorsibranchiatce or Errantes, including the Sea-Centipedes 

 and Sea-Mice. 



2. The Tubicohf, which include those that live in tubes, as the 

 Serpula. 



3. The Terricolcf, inhabiting the earth, including the Common Earth- 

 Worm. 



4. The Suctorite, with suctorial disks, as the Leech. 



The order Dorsibranchiatce is named from the attachment of the 

 respiratory organs to the dorsal surface of the body, along the whole 

 or the greater portion of the length. All the species belonging to it 

 are aquatic and worm-like. They are active in their crawling, and 

 swim with facility. On account of this last faculty Milne-Edwards 

 has called them Errantes, to distinguish them from the next family, 

 which are characterised by opposite habits. Their head is distinct 

 from their trunk. They are furnished with two pairs of rudimentary 

 eyes. The body is sometimes very long, as in the case of the tropical 

 Nereids. [NEREIS.] It has however in the Sea-Mice considerable 

 breadth. This genus, the Aphrodita of Linnseus, may be taken as the 

 type of the order. 



Cuvier remarks that this genus is easily recognised among the 

 Dorsibranchiate Annelides by the two longitudinal rows of wide mem- 

 branous scales which coverthe back, and under which are hidden their 

 branchiae, in the form of small fleshy crests. Their body is generally 

 flattened in form, and shorter and wider than it is in the other 

 Annelides. Their very thick and muscular oesophagus is capable of 

 being extruded like a proboscis. They have an unequal intestine, 

 furnished on each side with a great number of branched caeca, the 

 extremities of which go to fix themselves between the bundles of 

 bristles that serve for feet. 



Savigny's HaHthcece consist of those which have three tentacles, and 

 between them a very small crest; they are without jaws. 



Example, JIalit/uea aculeata (Aphrodita aculeata, Linn.), the Sea- 

 Mouse. 



This is a very beautiful animal, and most superbly coloured. It is 

 oval, 6 or 8 niches long, and 2 or 3 iuclres wide. The scales of the back 



