Full resolution (JPEG) - On this page / på denna sida - I. Description of the developed (imaginal) stages of Chordeuma obesum n. g., n. sp.
<< prev. page << föreg. sida << >> nästa sida >> next page >>
Below is the raw OCR text
from the above scanned image.
Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan.
Ser du något fel? Korrekturläs sidan nu!
This page has been proofread at least once.
(diff)
(history)
Denna sida har korrekturlästs minst en gång.
(skillnad)
(historik)
Chordeuma obesum. The body is composed of a head (ce, cephalon), four thoracic
segments (th1—th4) and an unsegmented abdomen (g, ap) (postabdomen). The
headregion carries three pairs of appendages: antennules (a1), antennæ (a2) and maxillæ
(mx); every trace of mandibles and maxillulæ as well of eyes is wanting. That
my explanation of the appendages present is the correct one will be proved by the
developmental stages described below sub II.
The antennules (a1) are situated in front and somewhat ventrally on the rounded
head; they are short, clumsy and unsegmented, ovoid with two blunt terminal
processes and a smaller ventro-lateral spine nearer the base. On the ventral side of the
head, far behind the antennules. immediately in front of the upper lip of the mouth
(ul), and close together, are a pair of slender papilliform appendages (a2), also
unsegmented; the development shows that they are the antennæ; and besides there
seem to be rudiments of an antennal gland present at the base (if functional appears
doubtful, as I have not been able to find an excretory pore). The distal slender,
finger-like part of the antenna is clad with delicate adpressed hairs (at all events in
unripe specimens). The mouth-opening is protected in front by a small rounded
upper lip (ul), and close behind the mouth are the maxillæ (mx), proportionally
strong and with their bases almost meeting in the ventral middle line. These an the
largest and the only segmented appendages of the whole body, consisting of tree segments,
the terminal one forming a curved claw. The inner side of the large basal and
middle segments, and the front side of the latter and of the claw are provided with
similar spines and bristles as in the male (oomp. the description of the latter and
Fig. 12); the concave ventral side of the claw also carries a single large bristle.
Each of the four thoracic segments (th1—th4)has a pair of short, conical,
unsegmented feet, (p1—p4) looking almost like parapodia and set rather far apart; distallv
they often are curved like a (weak) claw, and in unripe individuals this terminal part
is sparsely beset with short hairs (PL II, Pig. 25). The anterior pair are somewhat
smaller and weaker than the rest, the posterior generally largest and strongest. Each
foot represents the stem and outer branch of the typical Copepod-swimming-foot, as
shown by the larva, and by the fact that often — and quite regularly in young
immature specimens — a papilliform rudiment of an inner branch (i) may be seen
on the second, third or fourth pair (Pl. I, Figs. 3, 6 i and Pl. II, Fig. 25 i).
The two posterior thoracic segments (th2, th3) are shorter and narrower than the
anterior, from which they are divided by a deep constriction, the latter as it were
more joining the head, the former the abdomen. In this constriction fits tightly the
membranous wall of the gall: that two compartments of the capsule are formed, the
posterior containing the hinder part of the female and its egg-mass, and in most
cases a male.
<< prev. page << föreg. sida << >> nästa sida >> next page >>
