It> TAiiK sko(;siu;i;(; 



Till' biiundarv between the prott)podite and the endopodite niiiy of course be tliought 

 of as being drawn in other ways as well; the alternatives described above seem, however, to 

 be those that are most probable. As I have already pointed out above, I have not succeeded 

 in deciding which of these two alternatives have the strongest argunicnts to su2)port tlieiu; 

 1 know of no forms so far that give any clear evidence on this point. 

 ihsiorirai. .Most of the authors who have dealt with this group of Crustacea are very sujjcrficial with 



regard to this important problem. Thus, for instance, no one has tried so far to identify the 

 different joints of the protopodite; the terms jjrocoxale, coxale and basale have not come into 

 use for this group. 



The vibratory plate has — if its uu)rj)hok)gical value has been touched upon at all — 

 been taken by most investigators to be the exopodite, and the distal part of this limb, wliich 

 often points backwards, has been taken an endopodite. With regard to the exact boundary 

 between the protopodite and the endopodite these writers are very vague, and one cannot 

 tind any definite statements in their works on this point; most of them seem, however, to have 

 taken the forward pointing processes on the antero-ventral part of this limb as belonging to 

 the protopodite. 



The only one of the previous authors who has sought to enter more deeply into this 

 difficult problem is G. W. Mt'LLER. Leaving aside the opinion of this writer as expressed in 

 earlier works — which seems to me of little interest in this connection — I shall give an account 

 here of his view as expressed in his monumental work of 1894, a view that he did not depart 

 from in his later works. According to this investigator the vibratory plate on this limb is to 

 be taken as an epipodial appendage in all families, „ohne damit eine Homologie mit dem 

 Epipodialanhang der Phyllopoda behaupten zu woUen, wie mir iiberhaupt die Homologie der 

 verschiedenen Epipodialanhange keineswegs sichergestellt erscheint" (G. W. MUller, 1894, 

 p. 85). The family Polycopidae: With regard to the fifth limb of this family G. W. MULLER — 

 the only investigator who has dealt in detail with the homologization of this appendage — 

 gave, as is seen above, p. 37, on the whole the same explanation as I have worked out above and 

 called the first method of explanation. This author does not, however, touch upon the question 

 as to wliich of the two distal verrucae corresponds to the exopodite and which to the endopodite. 

 The family Sarsiellidae: The large outer distal process corresponds to „den verschmoLzenen 

 beiden letzten Gliedern" (1894. p. 63) of the endopodite; no information is found in this author's 

 works as to the morphological value of the small inner distal process. The family Cypridinidae: 

 The joint or the two joints on which the vibratory plate is fixed was identified by G. W. MUllei{ 

 with the protopodite; all the following joints were homologized with the endopodite; the part 

 that, according to the first of the two methods of explanation given by me above, is homologous 

 with the first and second joint of the exopodite, is taken to be a single divided (bifurcated) 

 joint, the second joint of the endopodite. The family Asteropidae: G. W. Muller's idea of the 

 morphology of this limb has already been described above, so that I need only refer to this 

 account, p. 41 above. The family Halocypridae: The backward pointing branch is taken by 

 this writer as the second, third and fourth endopodite joints; the part that, according to tlic 

 first of the two methods of homologization given by me above, was interpreted as the endopodite, 



