256 



THE POPULAR EDUCATOR. 



connected to each other, and with nerve filaments passing from 

 the knots to their appointed places in the lobster's body. So 

 much might be seen by a rough examination of the lobster's 

 internal economy. Perhaps the prettiest thing in the whole 

 body is what is known as the gastric mill within its stomach, a 

 curious mechanical arrangement designed apparently to pound 

 up its food. The main parts of this crushing apparatus are 

 three teeth two of them parallel to one another, and the third 

 occupying an intermediate position. By putting certain parts 

 of the opened stomach together it is perfectly easy to see the 

 way in which these teeth are employed to crush material that 

 may be passed into the stomach. A remarkable feature about 

 these teeth, and one giving them considerable beauty, is their 

 colour. Of a yellowish brown on their crushing surfaces, they 

 gradually become of a delicate bluish green towards the base. 

 The external colour of animals is usually supposed by 

 naturalists to subserve some useful end, but it is hard to see 

 what may be the utility of the hidden colouring of a lobster's 

 gastric mill. 



The common lobster (Homarus vulgaris) is a familiar enough 

 object around our coasts. It lives at the bottom of the water, 

 crawling over the bed of sand and rock, ever ready for any 

 prey that accident may bring in its way. 



There is a great demand for lobsters as an article of food, 

 to supply which the fishermen 

 lower wickerwork baskets down 

 into the water, marking their 

 position by means of buoys. 

 The lobsters creep into these 

 <l pots," as they are technically 

 termed, in search of the garbage 

 with which they are baited, and 

 being unable to get out are 

 captured when the pots are 

 hauled up. Perhaps no approxi- 

 mate estimate could be given 

 of the millions thus captured 

 every year for the use of man ; 

 and the destruction among 

 these crustaceans is further 

 increased by the fact that the 

 female lobsters have usually a 

 vast number of eggs under their 

 bodies in a more or less ad- 

 vanced stage of development, more than twelve thousand eggs 

 having been counted under the body of one female lobster. 



When these little eggs first appear they are extremely small 

 and black. They afterwards attain nearly to the size of ripe 

 elder-berries, and turn of a dark-brown colour. At the time of 

 laying the eggs the female bends up her body, and the eggs 

 thus become attached to a sticky substance which covers the 

 hairs of the abdominal appendages. They are thus carried 

 about until they become hatched. It must, however, be only 

 a small percentage of these eggs which produce young lobsters, 

 as it would appear that, although the eggs are laid at all times 

 of the year, it is only in the w,rm months of July and August 

 that they are hatched. This looks very much like waste in 

 nature, but the unhatched eggs may subserve some useful 

 purpose unknown to us. 



There is a marked inconvenience attending the possession of 

 an outside skeleton, enclosing the animal as if in a rigid box. 

 The lobster must grow, and accordingly it periodically casts 

 off its hard coat. According to some authors this moulting 

 appears to be rather a trying operation ; for when the animal is 

 going to cast off its old suit, it retires from the open parts of 

 the sea, and seeks out some retired place among the rocks 

 where there will be the least chance of interference on the 

 part of any enemies that may be roaming about. Its activity 

 ceases, and it is no longer voracious or quarrelsome, but 

 quietly awaits the favourable moment for effecting the change. 

 When that moment has arrived, it throws itself upon its back, 

 every limb seems to tremble, and the whole body is in violent 

 motion, while it swells itself in an unusual manner. At last 

 the shell begins to divide and is cast off, along with the cover- 

 ing of the eyes, the lining membrane of the stomach, and the 

 teeth connected with it. Even the casings of the legs and 

 claws are cast off as if they had only been top boots. A state 

 of exhaustion follows, during which the defenceless lobster lies 



LONGITUDINAL SECTION OF LOBSTEK. 



a, antenna; r, rostrum; o, eye; , stomach, in, intestine; A, heart; 

 (. liver; m, nervous ganglia; gl, sills; c,i, chief nervous masses ; ar, 

 a main blood-vessel. 



motionless and helpless, a prey to every marine animal that 

 considers lobster palatable. In the meantime, however, a rapid 

 process of restitution is going on ; for in about a couple of days 

 a new shell has been formed, and the animal has then obtained 

 a new suit. The number of its moultings per year depends on 

 its age, there being as many as six moults in the first and 

 second years of its life, four in the third year, and three in the 

 fourth year. 



In the information given thus far it will be perceived that 

 there is quite a community of facts respecting the crab, 

 described in a former article, and the lobster. Both are 

 animals enclosed in outside skeletons of calcareous matter 

 which they periodically cast off; both have ambulatory legs 

 and large claws ; each is turned from its natural colour when 

 boiled in water to the red so well known to inland dwellers, 

 many of whom erroneously regard the red colour of a boiled 

 lobster as its natural colour a belief which has probably given 

 rise to the well-known expression, "As red as a lobster." But 

 while there is much in common between the lobster and the 

 crab, there are many differences, which will be at once perceived 

 upon comparing the two animals side by side and part for part. 

 The divergence is much more wide than that which exists 

 between the lobster and the crayfish (Astacus fluviatilis). All 

 three animals are sufficiently alike to be included in the same 

 order, but the lobster and cray- 

 fish are really so much alike that 

 the same name astakos, the 

 Greek for lobster, was applied 

 to both until Milne-Edwards 

 suggested an alteration of names, 

 as the two animals were suffi- 

 ciently different to warrant it. 

 The name the lobster then re- 

 ceived was Homarus vulgaris, 

 and the crayfish retained its old 

 appellation of Astacus fluviatilis, 

 which means river lobster. 



The crayfish (Astacus fluviati- 

 lis) is a tiny little animal, seldom 

 exceeding four inches in length. 

 It is a sort of miniature lobster, 

 as a close examination of it exter- 

 nally and internally will prove. 

 Such an examination would lead 



to the discovery of certain differences between their gills and 

 abdominal appendages, &c., but generally they are so much 

 alike that one can understand naturalists half a century ago 

 calling them both lobsters, giving the name of "marine lobster" 

 to the Homarus, and " river lobster" to the crayfish. 



There is a great demand for the crayfish as an article of 

 food in France, where they are caught in a variety of ways. 

 The young crayfish is formed within the egg much in the 

 same fashion as a chick is formed within the hen's egg ; and 

 when it is hatched, the tiny crayfish presents a general resem- 

 blance to its parents. It is not so in the case of the crab and 

 lobster ; for here the young, when hatched, have to go through 

 certain changes before they attain to the mature form. 



Lobsters and crayfish can both see and hear, and are furnished 

 with peculiar organs for these purposes. The auditory organs 

 are lodged in the basal joint of the antennules. Here in each 

 antennule there is a bag containing clear [liquid, and projecting 

 into this fluid from certain sides of the bag there are a vast 

 number of minute hairs, which are in communication with 

 delicate nerve filaments. When a sound is produced, the 

 sonorous vibrations travelling through the water affect the 

 liquid contents of the bag, agitate the minute hairs, and con- 

 sequently the nerve filaments, thus giving rise to the sensation 

 of sound. 



The eye, both in lobster and crayfish, is entirely unlike the 

 eye of a back-boned animal. The free extremity of the eye- 

 stalk presents a soft, transparent, and convex surface, which is 

 divided into minute squares or facets by faint lines. It is one 

 of those compound eyes so often met with in other Crustacea 

 and in insects. Each of these facets forms a base for what is 

 called a visual pyramid, and within each of these pyramids 

 there are the elements required for seeing, which are probably 

 in connection with the optic nerve. It is a matter of dispute 

 how a crayfish sees with such eyes, but that it does so is certain. 



