MALE AND FEMALE LOBSTERS, SHOWING THE DIFFERENCE IN THE RELATIVE BREADTH OF THE ABDOMEN IN THE TWO SEXES. THIS FIGURE ALSO ILLUSTRATES THE DISSIMILARITY OF THE LARGE CLAWS AND THE FACT THAT THE "CRUSHING-CLAW" MAY BE ON EITHER THE RIGHT OR LEFT SIDE OF THE BODY

(From Brit. Mus. Guide)

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In the Lobster, as in many other Crustacea, the eggs are carried by the female until they hatch. After being extruded from the oviducts, they are attached by a kind of cementing substance to the swimmerets, where they hang in bunches. The swimmerets are kept constantly moving, so that the eggs may obtain the oxygen necessary for the developing embryos within. A female Lobster carrying eggs in this way is said by the fishermen to be "in berry," and may carry, according to its size, from about 3,000 to nearly 100,000 eggs. A period of about ten months elapses between the deposition of the eggs and hatching.

Fig. 8—First Larval Stage of the Common Lobster. × 4. (After Sars.)

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The young Lobster when first hatched ([Fig. 8]) differs considerably in general appearance from the adult animal. The abdominal somites have a row of spines down the middle of the back, and the telson has a forked shape. There are no swimmerets, but, as already mentioned, the legs bear large exopodites, which are used like oars, and by means of these the larval Lobster swims about at the surface of the sea. The claws or chelæ are at first hardly larger than the other legs, but later they increase in size, the swimmerets are developed, the exopodites of the legs are lost, and the young Lobster, sinking to the bottom of the sea, takes on the creeping habits and gradually assumes the shape of the adult.

In many Crustacea the changes of shape or metamorphoses undergone after hatching are much greater than in the Lobster. Some of these changes and their probable significance will be considered at greater length in a later chapter.