198 ON THE ANATOMY AND AFFINITIES OF 
2. In most Copepoda the eyes are so closely united as to appear 
single, and the region of the carapace which overlies them is not so. 
modified as to deserve the name of a distinct cornea. But in the 
genus Sapphiring (Plate XVI. [Plate 27] fig. 19), there are two 
small single cornee approximated together in the middle of the 
dorsal surface of the carapace ; and a still more interesting modifica- 
tion of the visual organs is presented by Coryceus (Plate XVI. 
[Plate 27] figs. 8, 9). Here two great, oval, spectacle-like, cornee 
are situated, one on each half of the anterior rounded margin of the 
carapace. 
3. The antennules and antenne vary very much in form. In 
many Copepoda they are so constructed as to subserve prehension, 
either for sexual or other objects. The antennules are thus specially 
modified in the males of Povtella and Cyclops, while in Coryceus 
these organs remain simple; but the antennz (III.’), are, in both 
sexes, converted into formidable weapons. It will be observed, 
however, that prehension is effected by the folding of the ultimate 
upon the penultimate joint, not by the biting of the apex of the 
ultimate joint against the prolonged distal angle of the penultimate. 
It is a subchela such as is found in A mphipoda and Stomapoda, not a 
chela like that of Podophthalinia and Pwcilopoda. 
4. The plate, which corresponds with the conjoined epistoma and 
labrum of decapod Crustacea, is very large in all the Copepoda | 
have examined. Its form and proportions in Cudanus, Coryceus, and 
Pontella are shown in (Plate XVI. [Plate 27] figs. 2, 9, 11). In 
the last-named genus it exhibits, as Milne Edwards has pointed out 
in his great work on the Craszacea, the remarkable peculiarity of 
being divided into three lobes, of which the middle is the smallest, 
and constitutes a kind of tongue-like projection (fig. 11). 
5. The metastoma of Calanus, as has been stated above, is ex- 
cavated anteriorly by so deep and wide an emargination, that it 
almost appears to consist of distinct lobes. In Portela, on the other 
hand, the metastoma is a large flattened plate, whose terminal 
emargination, though wide, is not deep (fig. 11). 
6. In Calanus, nine pairs of post-oral appendages have been 
found, the greatest number possessed by any masticating copepod. 
In Coryceus and Cyclops this number is reduced to eight, and of 
these the last is occasionally so much atrophied as to be hardly 
distinguishable. We have thus evidence of a certain tendency 
towards a diminution of the number of thoracic appendages in 
this order. 
The study of the development of the Copepoda shows that this. 
