A CENSUS OF LEG-JOINTS 43 



though it has been sti'ongly urged that one and the same 

 term ought to be applied to homologous parts throughout 

 the whole crustacean class, either nature has opposed the 

 rigid application of such a system, or the wit of man has 

 not yet been able to devise appropriate terms. 



It may here be mentioned that the full number of 

 joints for a malacostracan trunk-leg is seven. With a view 

 to uniformity of nomenclature, the afflicted naturalist has 

 for many years had to deal with these seven under the 

 following names : — Coxa, basis, ischium, merus, carpus, 

 propodus, dactylus, which respectively signify hip, foot, 

 socket of thigh joint, thigh joint, wrist, forefoot, and 

 finger or toe. Originally the names were longer, all being 

 podites, from coxopodite to dactylopodite, to the use of 

 which the philosophic French still adhere, though the 

 time-saving Anglo-Saxon has for the most part rejected 

 them. Among other difficulties in this terminology under 

 either form, it has to be remembered that the basis is the 

 second, not the basal joint of the limb. The more reason- 

 able plan is now being widely followed of naming these 

 joints simply according to their numerical order, the coxa 

 being called the first joint, and the dactylus the seventh. 

 But the older names have still to be borne in mind by 

 those who study the older literature. Even the numbers 

 are attended by a very unfortunate element of confusion. 

 The late Axel Boeck, when introducing the use of num- 

 bered joints, was studying the Amphipoda, in which the 

 first joint of a leg is seldom, if ever, free. Taking into 

 account, therefore, only the six free joints, he called the 

 second joint the first, and made the finger the sixth, instead 

 of seventh. In treating separately of the Amphipoda or 

 Isopoda, many naturalists have followed Boeck's usage as 

 reasonable and convenient. But when other Crustacea are 

 considered in which an appendage has the first joint or 

 perhaps all the seven joints free, they must be numbered 

 from one to seven, and w^ienever a comparison is needed 

 between the limbs of the Edriophthalma and those in 

 other groups, two different systems of numbering the 

 joints cannot fail to be highly embarrassing. It must 



