NATURAL HISTORY OF AMERICAN LOBSTER. 287 



the day after the molt, it was not possible to test the hypothesis outlined above, of 

 progressive changes following each molt. Przibram further expressed the belief that 

 similar claws in the lobster were due to regeneration, since in crabs individuals with 

 similar claws could be experimentally produced, a view confirmed later by the 

 experiments of Emmel, already referred to. 



Emmel (92) has described three additional cases in which abnormalities have been 

 artificially produced through the process of regeneration. In two instances similar 

 crushing claws resulted, and in a third case a triplication of the claw occurred in one 

 of the walking legs. This adds greater weight to the conclusion that all deformities in 

 the limbs of these crustaceans, as well as the condition of abnormal symmetry rarely met 

 with, may arise in nature through the process of regeneration, directed by some injur}' 

 or abnormal condition in the nerve end, the regeneration bud, or the growing or 

 developing limb. 



Monstrosities occur in the early and late embryos, and are therefore regarded as 

 congenital in their origin (see 14.9, p. 216). It is well known that embryonic or larval 

 monstrosities can be produced by subjecting the eggs of many animals to unnatural 

 and unfavorable conditions, and it is possible that the causes which produce a double- 

 headed larval lobster are similar to those which bring about the duplication of a big 

 claw in the adult. Perfect twins are occasionally produced from the same egg (see p. 321). 



Emmel has also recorded a striking case of the triplication of a big (right) crushing 

 claw in a lo-inch male lobster taken alive on the coast of Maine. The normal claw was 

 the smaller and transitional in type, while the two supernumerary claws were considerably 

 larger and typical crushers. Of these the outermost was an inverted right, with lighter 

 colored surface uppermost, and the other a normally disposed left. The abnormal 

 chela was removed by autotomy, in anticipation by the experimenter of some interesting 

 results at the next regeneration, but to the regret of all students interested in the problems 

 of regeneration this animal died in September, 1906. 



Emmel remarks that if the dupUcation of the big claws and other similar deformities 

 which appear in the lobster were congenital in origin, we should expect to meet with cases in 

 the larvae and the later stages of growth, but after an examination of over two thousand 

 fourth and fifth stage lobsters not a single abnormal case was observed. Examination 

 of thousands of larvae have everywhere given the same result. 



What was described in the newspaper press as a "lobster pearl" was taken from 

 a claw of a cooked lobster by Mr. F. W. Denton, of Hollis, Long Island. Through the 

 courtesy of Mr. Alfred Eno, of Jamaica, N. Y., the writer was able to examine this 

 interesting specimen,' an account of which, with illustrations, has been published (see 

 137). The "pearl" is a globular body 11 millimeters in diameter and of the same 

 creamy tint as the inside of a lobster's shell, with which it agrees in every physical and 

 biological character. ** It probably represents a freak of the regeneration process fol- 

 lowing injury to the claw, and a more or less permanent invagination of the skin at a 

 certain point. It is safe to say that no true pearl can be formed in any arthropod. 



" Dr. W. T. Caiman, of the British Museum, writes under date of January 14, 1911, that a similar specimen was received 

 from a fishmonger in London several years ago, but in this case the body was "embedded in the abdominal muscles of 

 Palinurus valfforis," and is now preserved in the Museum of the College of Surgeons. 



