habitat, and possess a greater degree of vitality or ability to live without food than related forms in what may be considered more favorable regions, and through and by reason of their long sleep or hibernation (more properly æstivation), with its inactivity and consequent immunity from any waste or exhaustion of vital strength, are enabled to maintain their hold upon life when animals more highly organized would inevitably perish; and we are furnished with an illustration in the instances cited, how nature works compensatively, when we institute a comparison with the opposite condition of activity, and the food required to sustain it.

BARNACLES.

BY J. S. KINGSLEY.

UAINT old Gerarde in his Herball, or Generall Historie of Plantes, says, on page 1391, "We are arrived to the end of our historie, thinking it not impertinent to the conclusion of the same, to end with one of the marvels of this land (we may say of the world). . . . . There are founde in the north parts of Scotland, and the islands adjacent, called Orchades, certaine trees whereon doe growe certaine shell fishes, of a white colour, tending to russet, wherein are contained little living creatures; which shels, in time of maturitie, doe open, and out of them growe those little living things which falling into the water doe become fowles, whom we call Barnakles, in the North of England Brant Geese, and in Lancashire Tree Geese: but the other that doe fall upon the land perish and come to nothing." He then goes on to describe in detail the various transformations by which the barnacle is changed into a goose, saying, "But what our eies have seene and hands have touched, we shall declare." He tells us that when the bird is formed in the shell, the latter gapes, the legs hang out, the bird grows larger, until at length it hangs only by the bill and soon after drops into the water, "where it gathereth feathers and groweth to a fowle bigger than a mallard and lesser than a goose.'

A quotation in Walton's Complete Angler repeats the same curious notion:

"So slow Boötes underneath him sees

In th' icy islands goslings hatched of trees,
Whose fruitful leaves falling into water
Are turned tis known to living fowls soon after.

So rotten planks of broken ships do change
To Barnacles. O transformation strange!
'T was first a green tree, then a broken hull
Lately a mushroom, now a flying gull.”

The transformations described by the above authors are, it is needless to say, founded wholly upon fancy, but the metamorphoses observed in a study of the life-history of a barnacle are scarcely less wonderful than those so minutely related by the old botanist. The old idea is still perpetuated in the names of two animals that of the "Barnacle Goose" (Bernicla), and in the specific name of one species of barnacle, the Lepas anserifera of Linnæus.

Barnacles were at first classed among the Mollusca, on account of their calcareous valves, as were at a later date the Brachiopoda; but in 1828-29 John Thompson proved, by studies of their embryology, that they had absolutely no molluscan affinities, but that they were Crustacea. Later investigations of their anatomy have confirmed this and they are now accorded a place among the lowest Crustacea, the Rhizocephala only being below them.

They form the sub-class Cirripedia, and are divided into two orders: the first is the pedunculated Cirripedia, in which there is a capitulum, generally formed of calcareous valves, varying in number, and united by membranes, and a tough leathery stalk, the peduncle, by which they are attached; in the other order, the sessile Cirripedia, the capitulum has four or more of its valves immovably united, and is directly attached without the intervention of a peduncle.

In Figure 5 we give the anatomy of one of the pedunculated forms, Lepas fascicularis of Ellis and Solander. In this species the capitulum is composed of five valves, two on each side, and one on the dorsal edge. The ventral margin is open and the two basal valves are connected by an adductor muscle (A, e), by which this opening can be closed. To dissect a specimen, it should be placed under water in a wax-bottomed pan and pinned down. In this manner the parts float out and the various organs are easily seen. The valves of one side are removed by cutting the adductor scutorum muscle and the membranes uniting them. This discloses a body with six pairs of long ciliated arms, the cirri (A, e), which represent the thoracic feet. Each cirrus consists of a basal portion and two long jointed branches. They decrease in length as we go forward (that is, toward the peduncle). In front of these cirri we find a protruding organ formed by the

mouth parts (A, m). These consist of an upper lip to which is attached a so-called palpus (B, 1). Next follow the mandibles (B, 2). Then the two pairs of maxillæ (B, 3 and 4). The maxillipeds, which are found in the higher Crustacea, are wanting. At the base of the first cirrus arise processes, varying in number in different species, which are termed filamentary appendages (A,f). These have been supposed to be part of the respiratory apparatus, but that such is their sole function is at least doubtful.

(FIG. 5.) ANATOMY OF LEPAS FASCICULARIS.

Between the sixth pair of cirri are found two small processes consisting of one or more joints, called the caudal appendages, and representing the abdomen of the higher Crustacea. Beneath these arises a long slender organ, the male intromittent organ (A, p).

On opening the body, starting from the mouth, we see first a slender tube, the esophagus, then comes the stomach (A, 8), which connects without any defined constriction with the intestine (A, i), and terminates at the vent (A, a), between the caudal appendages. At the anterior part of the stomach are seen the hepatic openings (A, h) which connect with the liver

(A, 1). The circulatory system is very imperfect. There is a dorsal vessel (A, d) which I have succeeded in injecting; the blood flows between the muscles in broad currents and is not confined in closed vessels. Respiration is probably performed by the whole surface of the body. The barnacles are generally hermaphroditic. The testes (A, t) are found surrounding the alimentary canal and extending into the filiamentary appendages and the bases of the cirri; they consist of branching tubes connecting with lobular cæca. The Vasa deferentia (A, v) are disposed one upon each side. They follow an undulating course and unite at the base of the penis (p) and proceed as a single tube to the end. The ovaries are found in the peduncle (A, 0) and present the same general appearance as do the testes.

The nervous system is easily dissected by laying the specimen upon the dorsal surface (after removing all the valves) and cutting away in front of the oesophagus. This will expose the supra-oesophageal ganglia (C, 8), which will be readily recognized, as they present the same shiny white appearance that always characterizes nerves. From the commissure connecting these ganglia a single nerve arises and proceeds forward in the median line. The optic nerves originate on each side, have each an enlargement, the ophthalmic ganglion (C, o) and unite in the rudimentary eye (C, e), which is imbedded in the membranes of the body. Exterior to these arise the nerves which supply the peduncle. From the posterior angles of the supra-œsophageal ganglia a nerve on each side (C, ∞) passes backward around the œsophagus and unite in the infra-esophageal ganglion (C, n). From the anterior portion of this arise the nerves which go to the adductor-scutorum (C, a) muscle; on the sides. the nerves which go to the first pair of cirri have their origin; from the dorsal surface (the under surface as the specimen lies) are given off two nerves which are distributed among the viscera. The second, third, fourth, and fifth thoracic ganglia follow each other, are connected by commissures, and give rise to nerves supplying their respective cirri. The sixth ganglion is almost invariably united to the fifth, and from it arise the nerves going to the sixth pair of cirri and the penis. In one specimen, however, I have found the fifth and sixth ganglia connected by distinct commissures.

.

In the sessile Cirripedes the internal anatomy does not differ greatly from the form above described. They are best dissected by removing the animal through the base (the portion by which

they are attached), breaking it down if it be calcareous. One curious feature of both orders remains to be noticed, namely, two glands in the peduncle which secrete a cement by which the animals attach themselves.

We have said above that the barnacles are generally hermaphrodites. In the case, however, of the genera Ibla and Scalpellum, this is not strictly the case. In the species of these genera occur specimens of the normal hermaphroditic form, and also females in which the penis and testes are wanting; next we have curious male forms. Certain of these (complemental males they are called) are parasitic upon the hermaphrodites while others are attached to the female individuals. In both cases they live just within the (FIG. 6.) valves and are attached either to the valves or the IBLA, MALE membranes of the body. These males are imper

ENLARGED.

fectly developed, in some cases without mouth or alimentary canal, in others there is a long and flexible peduncle, and in still others it is not differentiated; the male genital organs aare developed, but with the penis short or wanting. (Figure 6, male of Ibla Cumingii, from Darwin). This great difference between the sexes has its analogues in the Cephalopoda, where the males of certain species were first described as parasitic worms, and in the Lernean Copepoda, Olyan which are closely allied to the Cirripedia.

Recent investigators have

shown that close fertilization But is the exception, not the rule,

Thompson.)

a, Males lodged within the valves.

among plants. and here seems to be a case in the animal kingdom, where nature plainly shows her preference for cross

fertilization. In those genera which are strictly hermaphroditic,