NATURAL, HISTORY OF AMERICAN LOBSTER. 207 



be next to impossible for it to be withdrawn without rupture. The older naturalists 

 used to explain the withdrawal of the large claws by a wasting of the tissues. The 

 lobster was supposed to become sick and emaciated, which was, of course, an error. 

 The most significant fact in this process is the displacement of the liquids which nor- 

 mally belong to these appendages. The terminal soft tissues of the claw are essentially 

 a sponge work of involuntary muscle fibers, to which the returning blood stream has 

 free access. 



The changes in the armature of the lock forceps, which attend each molt in both 

 young and adult, are discussed in chapter vii. 



MOLTING OP THE " HAMMER" CLAW IN THE SNAPPING SHRIMP, ALPHEUS. 



It would be erroneous to infer that all relatives of the lobster in molting with- 

 draw the flesh of their big claws through the "drawplates" of the basal segments of 

 the limb. This is not true of certain species of the snapping shrimp, in which the great 

 "hammer" claws are proportionately larger than in the lobster. 



On November 13, 1896, while at the zoological station at Naples, a large male of 

 Alpheus dentipes molted in a small aquarium at 3 o'clock in the afternoon. Prepara- 

 tions for this act had been going on for several hours, and were probably begun in the 

 early morning. In this case the muscular mass of the claw was withdrawn through a 

 crack, which extended along the outer margin of the propodus. This cleft was con- 

 tinuous, with a similar fissure involving the proximal segments of the cheliped and 

 extending through the basal ring. The great muscular mass of the hammer claw was 

 thus withdrawn without distortion. This fissure was assumed to correspond to a Unear 

 absorption area, but I have not been able to repeat the observation. 



CHANGES IN THE SKELETON PREPARATORY TO MOLTING. 



At the time of the molt there is an intermediate membrane which makes its appear- 

 ance between the new and old shells. It is noncellular, has a gelatinous appearance, is 

 very transparent, and may be found adherent to the old shell after the molt is past. 

 It bears the impress of a mosaic of cells, which can be none other than the cells of the 

 chitinogenous epithelium. Vitzou is thus in error in supposing that this substance is 

 a secretion of chitinogenous epitheUum underlying the new carapace, which it traverses 

 by endomosis. It must be either the first secreted product of the new shell or the 

 innermost layer of the old shell modified by absorption, if not derived from tegumental 

 glands. 



In this cuticular membrane the parts which correspond to the cell boundaries of 

 the chitinogenous epithelium have the form of elevated ridges on the under side, and in 

 the center of each polygonal area there is a slight thickening. Reaumur " had in view 

 a similar structure in the crayfish when he spoke of a glairy matter "as transparent as 

 water, which separated the parts which the crayfish was soon to cast off from the rest 



o Additions aux observations sur la mue des ^crevisses, M^moires de I'Academie Royale des Sciences, p. 263-274, i pL 

 Paris, 1719. 



