One of these projects upwards from
the middle of the back, a second downwards from the forehead, and
frequently there is a shorter one on each side near the posterior
inferior angles of the carapace. All these processes are, however,
wanting in Maia according to Couch, and in Eurynome according to
Kinahan; and in a third species of the same group of the Oxyrhynchi
(belonging or nearly allied to the genus Achaeus) I also find only an
inconsiderable dorsal spine, whilst the forehead and sides are unarmed.
This is another example warning us to be cautious in deductions from
analogy. Nothing seemed more probable than to refer back the beak-like
formation of the forehead in the Oxyrhynchi to the frontal process of
the Zoea, and now it appears that the young of the Oxyrhynchi are really
quite destitute of any such process. The following are more important
peculiarities of the Zoeae of the Crabs, although less striking than
these processes of the carapace which, in combination with the large
eyes, often give them so singular an appearance:--the anterior (inner)
antennae are simple, not jointed, and furnished at the extremity with
from two to three olfactory filaments; the posterior (outer) antennae
frequently run out into a remarkably long spine-like process ("styliform
process," Spence Bate), and bear, on the outside, an appendage, which is
sometimes very minute ("squamiform process" of Spence Bate),
corresponding with the antennal scale of the Prawns,* (* In a memoir on
the metamorphoses of the Porcellanae I have erroneously described this
appendage as the "flagellum.
Pages:
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63