March 10, 1905.] 



SCIENCE. 



375 



Whether this particular correlation exist 

 or not, Fasciolaria illustrates how remote 

 processes may affect the life of an organ- 

 ism, and how habits, apparently so useless 

 as the manufacture of infertile eggs and 

 imperfect spermatozoa, may be perpetu- 

 ated, since such habits may have indirect 

 results which, like cannibalism, are useful 

 to the species. 



The 'Great Forceps' of the Lobster: 

 Francis H. Herrick, Western Reserve 

 University. 



In the higher orders of Crustacea the 

 chief weapons of both attack and defense, 

 as well as for rending the prey, are the 

 pincers or ' forceps, ' borne on the first pair 

 of massive periopods. In both American 

 and European species two types of claw 

 are developed, irrespective of sex, on either 

 the right or left sides, the more primitive 

 toothed or lock-forceps, and the larger, 

 secondarily modified crushing claw. 



In a fuller paper I shall be able to offer 

 for the first time a complete history of the 

 curious periodic sequence (first noticed by 

 Starr in 1898), which occurs. in the spines 

 of the toothed claw, and which is apparent- 

 ly unique among animals— as well as of 

 the development of the two types of claw, 

 their structure, physiology and the changes 

 which ensue in molting. 



In the more slender lock-forceps the 

 teeth are arranged in a linear series, in 

 periods of eight. About midway in the 

 serrated margin of the 'hand' or larger 

 joint is a stout displaced spine of the first 

 order, which forms the 'lock' to the claw. 

 Upon closing, the dactyle falls on this spur, 

 and its teeth slide under those of the pro- 

 podus. It is thus firmly locked in this 

 position, so that no lateral motion is pos- 

 sible. To meet this adjustment the tips 

 of the claw are bent so that the dactyle is 

 overlapped ; the spines of the two joints are 

 further inclined in opposite directions and 

 aligned in a reversed manner. 



When perfect, the formula for each pe- 

 riod is as follows: 1 :4 : 3 :4 :2 :4 :3 :4 := 8. 

 About four periods occur between the tip 

 of the claw and the lock spine. The pri- 

 mary spines (1) are the first to arise, and 

 are consequently the oldest, as they are the 

 largest in the series. The primary spines 

 alone are developed as the first larval stage, 

 and tend to increase in geometrical ratio, 

 by the regular interpolation of new spines 

 between those already formed, in a linear 

 series. There is even a tendency to ad- 

 vance to the fourth progression, which if 

 effected would give periods of sixteen. 

 Spines of the second and third order begin 

 to appear in the third larva, while in the 

 fourth stage usually at least one eight- 

 period series is developed. 



During the larval stages tegumental 

 glands open by capillary ducts on the 

 proximal side of each spine, near its tip. 

 The tips of the claws develop like setae or 

 ' hairs. ' 



At the fourth stage both large claws are 

 similar and of the toothed type. Differ- 

 entiation of the crushing claw begins at 

 about the eighth molt, the large tubucles 

 being formed by a fusion of periodic teeth. 



The chelae abound in tufts of tactile 

 hairs, especially in early life, but show no 

 other peculiar sense-organs. The 'fine 

 meat' of the tips of the claws is a sponge- 

 work of involuntary muscle-fibers, to which 

 blood has access, and is adapted to meet 

 the needs of the molting period, when great 

 local changes in blood-pressure are de- 

 manded. 



The periodic sequence of the teeth in the 

 toothed type of claw may be regarded as of 

 incidental significance only, in increasing 

 the efficiency of a nicely adapted prehensile 

 tool and weapon. Cases of symmetry 

 which occasionally occur may represent a 

 reversion to the primitive and larval type, 

 in an incomplete stage in the reversal of 

 asymmetry, and therefore concerned with 



