REPORT ON THE COPEPODA. 131 



Forehead truncated, broad, and emarginate in the middle, posterior extremity narrow, but 

 only slightly tapered. Anterior antennas (PI. XLVIII. fig. 10) six-jointed, 1 slender, bearing 

 a few long and slender setae on the margin and apex ; posterior antennas longer than the 

 anterior, four-jointed, and very slender ; first, second, and fourth joints nearly equal in 

 length, third rather shorter, almost devoid of setas, except that the third joint has three on 

 the margin, the first and second each one, and the last three at the apex ; second foot-jaw 

 three-jointed, having a strongly falcate terminal joint; inner margin of second joint 

 having a boss-like dilatation near the apex (fig. 13) ; anterior foot-jaw (PI. XLVII. 

 fig. 13) rudimentary. The head and first three thoracic segments usually have a single 

 large oil globule situated near the lateral margin, and the three thoracic segments have 

 likewise each a similar globule in the middle line of the body. The caudal stylets are 

 long, linear, and closely adpressed (PL XLVIII. fig. 9, and PI. XLVII. fig. 14), bearing a 

 very short seta beyond the middle of the outer margin, and two small thorn-like apical setae. 

 The nervous system (PI. XLVII. fig. 16) may be seen with great distinctness in the pellucid 

 body of the animal, and consists of a ganglionic central (brain) mass, in which is embedded 

 a pigmented eye-spot ; from this centre are given off in all directions numerous nerve- 

 branches, the most conspicuous of these being supplied to the eyes, antennas, and feet. 

 The genital system (fig. 15) is also very conspicuous, the testis showing as along fusiform 

 organ on each side, connected by a broad vas deferens with the receptaculum seminis, 

 which opens into a cloacal pouch. 



Habitat. — The gatherings in which this interesting species occurred were from off 

 Kandavu, Fiji ; from the North Atlantic, in lat. 5° 28' N., long. 14° 38' W.; from 

 the North Atlantic, near Canary Islands (February 2 and 16, 1873); and April 

 28, 1876, near the same latitude; South Atlantic, in lat. 35° 25' S., long. 23° 40' W. 

 (Station 132). 



Amongst the distinctive characters insisted on by Haeckel as separating his two 

 species vitreum and pellucidum, one from the other, are the numbers of joints of the an- 

 terior antennas (four in pellucidum and six in vitreum), and the situation of the thickened 

 portion of the second foot-jaw (at the apex in pellucidum, at the base in vitreum). In 

 the Challenger specimens I have found the anterior antenna always six-jointed, except 

 indeed in some instances where the joints could not be very distinctly seen, and where 

 perhaps the limb might have been supposed to be four-jointed ; closer observation, how- 

 ever, seemed to reveal, though not very plainly, six joints. As to the structure of the 

 second foot-jaw, I have seen no instance of the basal thickening ; so that in these 

 specimens the antennal characters of vitreum (according to Haeckel) go with the jaw 

 characters of pellucidum. Claus, however, seems to have observed both species, and 

 endorses the characters given by Haeckel. The female is unknown. 



1 The antenna is shown in Plate XLVIII. fig. 10, as having seven joints : this is incorrect; the basal 

 joint should be removed. 



