156 CRUSTACEA EUCARIDA DECAPODA chap. 



breaking joint, the animal forgets to throw the injured leg or 

 stump off at the breaking joint, a proceeding which always 

 occurs under normal conditions. The regeneration of a limb 

 starts from a papilla which grows out of the breaking-joint, and 

 after a number of moults acquires the specific form of the limb 

 that has been lost. A number of interesting observations have 

 been made upon the regeneration of the limbs in Crustacea. It 

 was in the Hermit-crab that Morgan ^ proved that regeneration 

 and the liability to injury do not always run parallel, as 

 Weismann held they should, since the rudimentary posterior 

 thoracic limbs, which are never injured in nature, can regenerate 

 when artificially removed as easily as any others. Przibram "^ 

 has shown that in the shrimp Alpheus, whose chelipedes are 

 highly asymmetrical, if the large one be cut off, the small one 

 immediately begins to grow and to take on the form of the 

 large one, while the regenerated limb is formed as the small 

 variety. This remarkable inversion in the symmetry of the 

 animal clearly ensures that, if the large chela is injured and 

 thrown away, the least amount of time is wasted in providing 

 the shrimp with a new large claw. 



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 

 " Ijerry " 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 forljidding the sale of Lobsters 

 and Crabs " in berry " in 1 )oth 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 tlie larvae are hatched out approxiinately in the 

 following June. On liatching, 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 

 al)dominal limits), 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 tlie bottom, loses the 



1 Zool. Bulletin, i., 1898, p. 287. 

 - ArcUvfur Enlw. Mech. xL, 1901, p. 321. 



