274 DISCOVERY REPORTS 



The parts of the maxilliped of certain species of Serolis, as for example that of 

 S. glacialis, Tattersall (Fig. 2 d, e), might be interpreted in this way, but in some species, 

 for example S. schythei, Liitken (Fig. 2 b, c), the larger distal portion of the epipod, 

 instead of being freely articulated, is directly continuous with the proximal part of 

 the basis, whilst in S. iiototropis, n.sp. (Fig. 17 b), S. orbicidota, n.sp. (Fig. 15 «), 

 S. coritiota, Lockington, and S. exigua, Nordenstam (Fig. 2 a), this fusion is continued 

 beyond the articulation of the base of the endopod, so that the latter appears to spring 

 from the middle of a plate-like structure, which, according to Hansen's interpretation, 

 would represent the basis with its endite fused with the distal portion of the epipod. In 

 the two former species, S. nolotropis and S. orbiculata, the fusion of the endite {B') with 

 the epipod (£") is not as complete as in the two latter species. 



The question then arises whether this condition is a secondary one resuhing from the 

 fusion of the basis (5) with its endite {B') and the distal portion of the epipodite (£"), or 

 whether it might not better be interpreted as primitive, in which case the "distal portion 

 of the epipodite" {£') must be regarded as a lamellar outgrowth of the basis. If this 

 latter view is correct the condition met with in S. carinata, Lockington (Fig. 11 a), and 

 S. exigua, Nordenstam (Fig. 2«), is the most primitive; the next stage is represented by 

 S. orbiculata, n.sp., and S. fiotoiropis, n.sp. (Figs. 15 fl, 17 b), where the separation of the 

 endite {B') from the lamella (£") has begun ; and this is followed by the stage seen in 

 S. schythei, Liitken (Fig. 2 b), where the separation of the lamella (£") reaches as far as 

 the articulation of the endopod, but remains fused with the basis (B) behind this point. 

 In the final stage, seen in S. glacialis, Tattersall (Figs. 2 d, e), the lamella {£') is com- 

 pletely separated both from the basis (B) and its endite {B'). 



In connection with this point I have examined the maxillipeds of a number of the 

 more typical members of this order. In Cirolana borealis, Lilljeborg, the maxilliped 

 consists of a sympod made up of a small coxa and a larger basis produced distally into a 

 small endite; the palp consists of five segments, and a small epipod is also present, 

 attached to the coxopodite. In the female of this species, during the breeding phase, 

 a large lamellar outgrowth of the basis, exactly comparable in position with that of the 

 so-called " distal portion of the epipod " is developed ; lamella-like structures also occur 

 on the coxa and on the epipod, along the inner and lower margin of the former and on 

 the outer distal angle of the latter. Similar expansions also occur in the breeding females 

 of Eurydice elegaiitula, Hansen, Corallana antillensis, Hansen and Corallana tricor/iis, 

 Hansen, whilst in the female of Ceratothoa banksii. Leach, the lamella of the basis is 

 fused with the basis, producing a condition directly comparable with that of the maxil- 

 liped of S. schythei, Liitken. 



From these examples it seems reasonable to suppose that the "distal portion of the 

 epipodite" of Serolis is morphologically the same as the "lamella of the basipodite" 

 which is developed in the breeding females of the above-mentioned species, and that 

 the four stages represented by S. exigua, S. orbiculata, S. schythei and S. glacialis, 

 illustrate stages in the evolution of the appendage, in which the cumbersome structure 

 represented by the basis, its endite and lamellar outgrowth, is gradually replaced by a 



