Mnxilla. 



AM TAfiK SK()(iSI!i:i;C. 



is in thoso forms consititM-ably moiv stron<;ly (lovol()|n'il in tin- muli' .md iti .Hldilinn ili (Terences 

 are to \w obsorvoil in tlio propitrtions of tlio joints, in tlie develoiinienl iind eiiiiipinent ol the 

 bristles and in the basal spines, ete. This diMior])hisin seems ])resiimahlv to lie characteristic 

 of the genus as a whole. The fact that it has not been pinpcrh poiTited mil before is piobalilv 

 due to the rather superficial nature of previous investigators' observations, it is certaiidy true 

 that G. S. Bl;.\l'^ jioints out as early as 1868 b, p. 464, that the second joint on the e.xopodite 

 of the male second antenna is relatively longer than the corresponding joint in tlu^ female; 

 this statement is not found, however, in later works by this author. Of the other writers there 

 is only G. 0. Sahs, 1887, p. 20 who points out the existence of dimorphism: ,,Idetliele er 

 Svemmeantennerne hos Hannen kjendelig kraftigere udviklede end hos Hunnen, skjondt, iiaai 

 undtages Bigrenen, af et temmelig overensstemmende Udseende"*. 



W'itli regard to the endopodite of this antenna 6. 0. Sars, 1887, p. 19 states that this 

 branch is characterized by two bristles in the female, one the comparatively long end bristle 

 and the other a short bristle situated distally on the second joint. In a few cases a similar short 

 bristle has also been observed by me on the second joint, as will be seen from the descriptions 

 of the species given below; the bristle in (piestion is then attached at about the same place as 

 that where this joint of the male endopodite has three short bristles; it is presumably to be 

 considered as an abnormally appearing homologon to one of these bristles. There is no question 

 of any genus character. 



I might also point out in passing the abnormal type of the cndopt)dite of the female 

 second antenna that is reproduced on fig. 10 of A. norvegica and whose resemblance to the male 

 endopodite during the second larval stage is striking. In this type, which has been observed, 

 as a matter of fact, in other forms within the Cypridiniformes, though only very seldom, we 

 perhaps have a proof of the homology of the distal bristle on the female end joint with the 

 proximal bristle on the same joint in the male. 



In all the species of this genus that were investigated by me the epipodial appendage 

 of the maxilla was of about the same relative size and type. In the genus description given by 

 me this organ has also been stated to be of about the same type and relative size throughout 

 the whole genus. AU the reproductions of this organ that occur in the literature also show the 

 same size and type as was observed by me, with, however, one exception, G. W. MUller's 

 drawing, 1894, of A. teres, pi. 5, fig. 15. In this figure this organ is drawn consi- 

 derably smaller than I found it and its type is also somewhat different. I did not 

 make any reservation for this species in my general genus description because there seemed 

 to me to be strong reasons to believe that G. W. MlIller had made a mistake on this 

 point either by drawing incorrectly or by taking an abnormal specimen as a type for the 

 species. As will be seen from the remark under the species A. Mullen described below, 

 one specimen of this species from the Gulf of Naples, determined by G. W. MOller as 

 A. teres, had a maxiUa with an epipodial appendage of quite the same type as I found in 

 all the other species of this genus. 



* On the whole the natatory antennae in the male are obviously more powerfully developed Ihiiii in Ihe female, 

 though, with the exception of the endopodite, they agree fairly well in appearance. 



