FIG. 5. The mouth-parts of the Honey-bee, Apis mellifica, worker. Drawn from a specimen as seen from the aboral surface and removed from the head.
a-d'. Parts of the labium.
a. The lingua or tongue: a long, narrow organ covered with setae, which are arranged in transverse rows, and increase in length from the base to the apex of the tongue. In every fifth row there are touch (?) papillae mingled with the setae. The tongue ends with a concave disc, the aboral surface of which carries branched hairs. The whole aboral surface of the organ is traversed by a longitudinal groove. The sides of the groove are thin, but its floor is thickened, forming a grooved rod, which extends as far as the terminal disc. The groove and rod appear to be of functional importance in the act of gathering honey.
b. The four-jointed labial palp. The basal joint is long and grooved internally. The groove assists with the lingua to make a channel along which the honey flows. Between the bases of the palpi and lingua lie the paraglossae.
c. Mentum. The duct of the salivary gland opens on its inner surface at the root of the tongue and beneath a small valve.
df. Lora of Kirby and Spence (Introduction to Entomology, vol. iii. 1826, p. 367), commonly found in Hymenoptera. It supports the submentum centrally, and at each extremity it is connected to the cardo of the maxilla. It pushes forwards the sub-mentum, mentum, etc, when the mouth-parts are protruded for the purpose of suction.
e-g. Parts of maxilla.
e. The lacinia, e' the palp, f . The stipes and g. The cardo of the maxilla.
The palp is generally stated to be one-jointed. It appears to be really imperfectly two-jointed. In some Apidae it has as many as six joints. h. The Mandible. Its inner surface is concave, and bears two oblique ridges on which hairs are implanted.
When the mouth-parts are at rest the tongue is partially retracted, and together with the labral palpi and laciniae of the maxillae are recurved within the mouth. The sub-mentum, lora, and cardines of the maxilla are folded upon one another at the same time and hidden by the large mentum.
Briant, J. L. S. xvii. 1884.
Cook, Amer. Naturalist, xiv. 1880.
FIGS. 6-9. Appendages connected with the mouth, and Fig. 10, the first pair of ambulatory limbs of Scolopendra morsitans, after Savigny, Memoires sur les Animaux sans vertebres, Part I, Paris, 1816. Slightly altered from a specimen.
6. Mandible: a. small three-jointed palp.
7. Maxilla, consisting of a small soft external 'palp' and a median lobe which, as in Myriapoda Diplopoda, e. g. Iulus, is fused basally with its fellow.
8. Palp-like limb. In Scolopendra audax, according to Pagenstecher (Allgemeine Zoologie, ii. 1877, p. 1 31), it consists, like an ordinary walking limb, of seven joints. a. Basal joint fused to its fellow, b and c. two median joints, d. Claw terminated by two to three spines; e. the sternum (?) displaced laterally.
9. Poison claw. a. Appears to represent the enlarged basal joint fused to its fellow medianly; its anterior edge is produced into a process bearing several stout spines, b. Joint prolonged internally into a spine-bearing process, c. Two folds in the soft membrane connecting b with d on the inner edge. They do not appear to represent joints as they have been supposed to do. d. Large claw with the opening of the poison duct at its apex. It is hinged at its outer side upon b.
10. First pair of limbs, with seven joints. a, b, c, d. The seven joints.
It was supposed by Professor Rolleston that the double joints b, c, d are formed by division of the joints similarly lettered in Fig. 8. The terminal joint is generally regarded as a claw. It appears better not to use for these joints the designations coxa, trochanter, femur, tibia, and tarsus. They are all similar in aspect, not distinctly differentiated in shape as are the parts so termed in Insecta. e. The sternum. There is no tergum to this somite unless it is united with the tergum of the preceding somite.
The appendages, Figs. 8-10, are generally regarded as belonging to what is called the 'basilar somite.' But the appendage, Fig. 8, is distinctly connected with the head, and represents the labium of Insecta. In no Chilopod that I have examined is a tergum present corresponding to the limb, Fig. 10, and in some species this limb is absent. Balfour (Comp. Embryology, i. p. 325) is inclined to doubt the correctness of Newport's statement to the effect that the basilar somite is composed of four embryonic somites to which the appendages Figs. 8-10 belong, one of the somites being limbless. He believes that the basilar somite corresponds to the poison claws, Fig. 9, alone, and that there is no somite without a limb. At any rate there is none in Geophilus, according to Metschnikoff.
Cf. Meinert, Caput Scolopendrae, Copenhagen, 1883; cf. Journal R. Micr. Soc. 1884, p. 374, and Amer. Naturalist, xviii. 1884.
Poison glands. MacLeod, Bull. Ac. Roy. Belg. (2) xlv. 1878.
FIG. 11. Geometrical Spider, Epeira fasciata, viewed from below. Regne Animale, Les Arachnides, by Duges and Milne Edwards, P1. XI. Fig. \b.
a. The chelicerae or falces. These limbs are post-oral in the embryo but prae-oral in the adult. They consist of a large basal and a slender claw-like terminal joint, at the top of which opens the duct of the poison gland, seen at f, in Fig. 12. This joint moves horizontally in all Spiders with the exception of the Tetra-pneu-mones (Mygale and the Trap-door Spiders).
b. Pedipalpi, consisting of a limb-like terminal portion and an enlarged basal or masticatory joint. Between the two basal joints is the lower lip or labium of authors. It has nothing to do with the parts so termed either in Insecta or Scorpio, but represents the prosternite (cf. Ray Lankester, Q. J. M. xxi. 1881. p. 531, and Fig. 9, B). The specimen from which this figure was taken was that of a female. In the male the terminal joint of the limb-like portion or 'palp' of this appendage is modified to receive the sperm and act as a copulatory organ.
c. Mesosternite, surrounded by d. The basal joints of the four ambulatory limbs.
The part of the body bearing the above-described limbs constitutes the cephalo-thorax. It is followed by the soft unsegmented abdomen which, in the embryo Spider, consists of nine somites and a terminal azygos piece.
e. The stigmata leading to the two pulmonary sacs.
f. Those leading to the tracheae. Between them is the epigynal organ covering the sexual aperture.
g. The four spinning mammillae with the anal valve as a fifth lobe behind. Most Spiders, with the exception of the Tetra-pneumones, have six mammillae. The Tetra-pneumones, as a rule, possess only four.
Auditory and olfactory organs. Dahl, A. M. A. xxiv. 1885; cf. A. N. H. (5) xiv. 1884. On an organ of sense. Bertkau, A. M. A. xxiv. 1885, and Id. and Schimkewitsch, Z. A. viii. 1885.
Respiratory organs, MacLeod, Archives de Biologie, v. 1885.
FIG. 12. The digestive apparatus of Tegenaria domestica, the common House Spider, after Plateau, Bull. Acad. Roy. Belg. xliv, PL I. Fig. 2.
a. The anterior part of the cephalo-thorax, carrying the eight uni-corneal or mono-meniscous eyes arranged in two transverse rows.
b. Second joint of the right pedipalp.
c. Peduncle connecting the cephalo-thorax with the abdomen.
d. The basal joints of the four pairs of ambulatory limbs.
e. Two of the six spinning mammillae.
f. The poison glands. Their ducts open on the terminal joint of the chelicera (a, Fig. 11).
g. The anterior caecum of the cephalo-thoracic stomachal dilatation used in sucking up the juices of the prey. In front of it are the muscles of the pharynx; behind it, the dilatator muscles of the stomach; and at the sides it gives off, • h. The caeca, eight in number, which enter the bases of the limbs and are recurved in the coxal joint. i. The chylific or abdominal stomach receiving j. The numerous ducts of the so-called liver or hepato-pancreas which secretes a digestive fluid. These ducts are numerous in Arachnida, and the glands large. k. Caecum, opening on the dorsal side of the proctodaeum or rectum at the point where the ramified Malpighian tubules, shown as white lines in the figure, enter it.
Fore-gut and digestive organs in Arachnida. MacLeod, Bull. Acad. Roy. Belg. (3), viii. 1884.
Structure and function of Liver. Bertkau, A. M. A. xxiii. 1884; xxiv. 1885. Cf. Dahl, Z. A. viii. 1885.
Anatomy of Epeira. Schimkewitsch, A. Sc. N. (6) xvii. 1884. Development. Id. Z. A. vii. 1884.
FIG. 12. Nauplius of Lepas fascicularis. Von Willemoes-Suhm, Ph. Tr., 1876, PL X. Fig. II.
This Nauplius was taken in the Pacific Ocean during the passage of H. M. S. Challenger from Japan to the Sandwich Islands. It is but just hatched from the egg, and is still enveloped in a larval skin, destined to be shed in a few hours. In size it measures about 1/75 of an inch. In subsequent stages of the Nauplius form it grows immensely in size and acquires long dorsal, caudal, and ventral spines. It was originally described by Dohrn as Archizoaea gigas.
a. The first uniramose appendage. It represents the first antenna, and in the Cypris-stage of the Barnacle becomes four-jointed. The second joint bears a suctorial disc, in the centre of which opens the duct of the cement gland. By means of this apparatus, the Cypris-like animal attaches itself to some foreign body. The terminal joint bears olfactory hairs, and, together with the third joint, is discarded in the pupa-stage.
b. The second appendage, a biramose swimming foot. It represents the second antenna of other Crustacea, but in the Cirripedia is completely lost in the Cypris-stage.
c. The third appendage, also biramose. It represents the mandible, but in the adult is reduced to a toothed lobe. These three appendages are segmented from the first in this Cirriped. In some others they are at first unjointed. The protopodites of the second and third limbs bear hook-like masticatory processes. The second has such a hook also in the Nauplius of Branchiopoda and Copepoda.
d. The immense labrum or upper lip.
e. A groove on its under side (Balfour), not the oesophagus, as was supposed by von Willemoes-Suhm.
f. Points to the unpaired dorsal eye characteristic of the Nauplius. It is retained throughout life in the Copepoda. In this stage it has a distinct lens. At the third moult there appears on either side of it a two-jointed sense organ similar to the sense organ of the Branchiopoda, and in subsequent stages a compound eye also appears on either side of it, to be lost in the pupa-stage. The two granular patches on either side of the eye are the rudiments of the cerebral ganglion.
g. The intestine.
h. Points to the position of the anus which lies between the caudal and ventral spines. These spines are at present in a compressed state within the larval cuticle. The dorsal spine is developed at the third moult The spines are probably a secondary adaptive protection, and are not connected with the spines present in a Zoaea.
i. The lateral processes of the cephalo-thoracic carapace to which also the caudal spine belongs. These lateral processes, after the first moult, are disposed horizontally outwards, and form the anterior outer angles of the triangular carapace. They are hollow and give exit in an older Nauplius to the ducts.of glands situated under the carapace, as do other shorter processes developed on the margins of that structure.