COPEPODA 



most species. The pove in the third basipodite is generally wanting, and so are the two proximal 

 pores in the third segment of the exopodite (of. pi. II fig. 5 a); in several species the pore of the 

 Re I is wanting in the second pair of legs, bnt very seldom in the third and fourth pair; this kind 

 of pores was never found in the first pair of legs and is wanting in the fifth pair in species, in which 

 this pair is of no use for natatory purposes. In the Scolfcithricidae the pores are generally poorly 

 developed. To illustrate the differences which may be found in species, which really are very nearly 

 related I refer to the differences in Chiridius aniiattis^ nasittiis and modestus (cf. pi II fig. 3 a, 4 a 

 and 5 a); the greatest development of the glands and pores is found in Euchirella^ in E. rostrnta and 

 iiicssi)iciisis the usual pore at the base of Se Re I pes. Ill was present, but in E. curficauda it was 

 wanting. The number of pores in the adult and the young ones of the penultimate stages are gene- 

 rally alike, but in EucJiirclla rostrata the pore, which is found at the base of Se i Re III pe.s. II — IV, 

 is wanting; the younger stages have the number of pores more or less reduced as realised in the 

 decription of the different stages of, f. inst, Calamts fir^narchicus. 



In addition to the mentioned system of pores, a small pore sorrounded by delicate hairs is 

 found on the anterior surface of the third segment of the endopodite in the second to the fourth pair 

 of legs (cf. pi. I fig 3e; pi. VIII fig. 18 c). 



Pores arranged in a characteristic way (pi. I fig. 3 f — g) are found in Megacalanus and Alacro- 

 calanus^ to the description of which I refer. 



In the first pair of legs pores are often found in the outer margin of the exopodite (cf. pi. VI fig. 2 a). 



The mouth of the Copepods shows within the different groups a very different structure, well 

 adapted for the habits of the animals; as far as the parasitic or semiparasitic forms are concerned 

 fairly good descriptions are found in literature. 



The Plancton-Copepods probably nourish on extremely small plants as well as on bigger ones, 

 which are extremely well masticated, in a way that the shells or fragments of Diatomes, f. inst, are 

 very seldom found so well preserved, that their exact nature could be determined (cf. Dakin). 



The first and I think the most exhaustive account of these organs in one of the Calanoida 

 has been given by Moebius for Eiicha'te norvegica^ his carinata (1875 p. 271; tab. VII); Clans has (1863 

 p. 25) given a short, but not very good description of the structure in PUiiroiiiiua, but the following 

 quotation indicates, that he has examined the structure in other forms as well. 



»Auf die zahlreichen Modificationen, welche in den einzelnen Gattungen eintreten, im speciellen 

 einzugehen wiirde zu weit fiihren und nicht das geniigende Interesse bieten, zumal diese Bildungen 

 wegen der Schwierigkeit ihrer Untersuchung nicht leicht systematisch zu verwerthen sind.« 



In all the Calanoida aiiiphascandria^ examined by me, as well as in several of the heterarthrandria^ 

 f. inst Plcitroinvia^ Metridia, Temora, Batltypontia, and with a few not very important modifications 

 from a morphological point of view in Liicicuta^ Anomalocera and Acartia, the mouth-organs show 

 the following structure. The opening of the intestinal duct is placed between a prominent labrum 

 and less prominent labium, on each side bearing a labial lobe, corresponding to the paragnatha of Clans; 

 the labrum and the labium are on each side connected with a chitinous framework, which forms a 

 bridge over the manducatory part of the mandibulae, and in a way forms the lateral limitation of the mouth. 



