To return to the Lobster; for the majority of the individuals there is a definite breeding season, viz. July and August, but a certain proportion breed earlier or later. A female begins to “berry” at about eight inches in length, and to produce more and more eggs up to about eighteen inches, when as many as 160,000 eggs are produced at a time; after this there is a decline in numbers. A female normally breeds only once in two years. Strict laws are enforced forbidding the sale of Lobsters and Crabs “in berry” in both England and America. The period of incubation, during which the developing eggs are attached to the swimmerets of the female, lasts about ten or eleven months, so that the larvae are hatched out approximately in the following June. On hatching, the larva, which measures about one-third of an inch, and is in the Mysis stage (_i.e._ it possesses all the thoracic limbs in a biramous condition, but is without the abdominal limbs), swims at first on the surface. After five or six months of this life, during which the abdominal pleopods are added from before backwards, it sinks to the bottom, loses the exopodites of the thoracic limbs, and is converted into the young Lobster, measuring about half an inch in length. The little Lobster starts in deepish water, and gradually crawls towards the shore; here it passes its adolescence, but on coming to maturity it migrates out again into the deep water. =Fam. 2. Astacidae.=—In this family, which includes all the European and North American Crayfishes, _Astacus_ (_Potamobius_) and _Cambarus_, the podobranchs are united with the epipodites, the last thoracic segment is free, there is only one pleurobranch or none at all, the gills have a central lamina, but the filaments are without terminal hooks, and the endopodites of the first two pairs of abdominal appendages in the male serve as copulatory organs. For the distribution, etc., of these forms see p. 213. =Fam. 3. Parastacidae.=—This family includes the Crayfishes of the Southern Hemisphere, viz. _Parastacus_ from South America, _Astacopsis_ and _Engaeus_ from Australia, _Paranephrops_ from New Zealand, and _Astacoides_ from Madagascar. These genera agree with the Potamobiidae in the union of the podobranchs with the epipodites, and in the free condition of the last thoracic segment, but there are generally four pleurobranchs, the gills are without a lamina, the filaments have terminal hooks, and there are no sexual appendages in the male. For distribution, etc., see also p. 213. The larval development in the Crayfishes is still more abbreviated than in the Lobsters, the Mysis stage being passed through within the egg-membranes. The young, when they hatch out, are furnished with hooks upon the chelipedes, by which they anchor themselves to the pleopods of the mother. =Tribe 2. Eryonidea.= [Illustration: FIG. 105.—_Willemoesia inornata_, × ⅓. (From a figure prepared for Professor Weldon.) ]