ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 383 



The liiub may be cut off by the chelate walking-legs, and in the crayfish 

 by the chelffi themselves. 



In the hermit-crab the normal process of antotomy is the result of a 

 nuisegmental reflex, but if the animal be removed from its borrowed 

 shell, plucking with the chelte is necessary. The change of conditions 

 has necessitated the reinforcement of the unisegmental reflex by arcs of 

 higher levels, i.e. the reaction is plurisegmental. If the extensor muscle 

 to the second segment be cut, the hermit-crab proceeds to bite the 

 damaged limb down to the level of the breaking-plane in the second 

 segment. Thus, with modification of conditions, three types of reaction 

 to injury are exhibited — autotomy purely local, antotomy involving other 

 levels of the nervous system, and autophagy. 



In Galatheids autotomy can be performed by muscles at the base of 

 the damaged limb alone. The reflex is unisegmenttil, but under changed 

 conditions may be reinforced by arcs of other levels. 



In crabs autotomy is almost always a purely unisegmental reflex. 

 After injury, the extensors of the second segment, acting in opposite 

 directions on the ring of hard integument central to the breaking-plane, 

 cause weakening of the limb at this point, and division may take place at 

 once, as may be the case in Fortuiii/.s, ov \shen the distal part of the limb 

 meets an external point of resistance, usually the carapace. There is a 

 definite time-relation between the contractions of the opposing extensors. 

 In H//as, when no external point of resistance can be found, the animal 

 plucks off the damaged limb with its chelae. This is the only case in 

 which the unisegmental arc is reinforced from other levels. 



Morphological complexity seen in the structure of the breaking-joint 

 goes hand in hand with physiological specialization in the local or uni- 

 segmental arc. In Vertebrates the unisegmental reflex is regarded as 

 primary ; in Decapods the reaction is always unisegmental in the more 

 highly specialized forms. Evasion and hfemostasis are the fundamental 

 ends served by the self -amputation of limbs in Decapods. Autotomy is 

 always the outcome of a nocuous stimulus applied to the leg which is 

 abandoned 



Study of Fiddler-crabs.* — A. S. Pearse has made a study of Uca 

 piKjnax and U. piigilator at Woods Hole. They usually close their 

 burrows when the tide comes in. On a hard bottom they pull a round 

 piece of earth down over themselves ; on a soft bottom they plaster up 

 the opening somewhat, then enter the burrow, and, after pulling the 

 mud down with the legs, push up material from below. Male fiddler- 

 crabs try to induce the females to come to them by waving their 

 chelipeds, and then try to make them enter the burrow. They use the 

 great chela as a weapon for combat and defence and as a signal to 

 attract the females. They do not use it as a stopper to tlieir burrows, 

 nor to dig, nor as a " nuptial couch " during copulation. 



Two Amphipods from Luzon.!— C. F. Baker describes Parorchestia 

 luzonensis sp. n. from the summit of Mount Maquiling, under stones 



* Trans. Wisconsin Acad. Sci., xvii. (1914) pp. 791-802 (7 figs.). 

 t Philippine Journ. Sci., x. (1915) pp. 251-5 (3 pis.). 



