their mode of attachment that we must consider them together. In the bee they are slung upon a long retractile framework with elbows and hinges. I shall call this framework the "maxillary suspensorium;" all the published drawings of it that I have seen are grossly inaccurate, save that of Dr. Wolff, and even he seems to have missed some of the most interesting points. The basal part, or basicranial rods (BR in fig. 5), are inserted close to the roots of the mesocephalic pillars, in front of the occipital foramen. The rods run forwards towards the oral opening, the basicranial wall being excavated so as to allow them full play. They slightly ascend when the mouthparts are retracted (BR in fig. 2), and are nearly horizontal when the proboscis is extended. They are united to the rim of the excavated part of the basis cranii by a web (just as the mesocephalic pillars of Cicada are joined to the sidewall). They are rigidly inserted at their roots, and are slightly elastic above, while their motion is limited by the web. (The two basicranial rods are bound to each other by a still more delicate web which forms the limiting wall of the head at the excavated part, and yet permits the play of the suspensorial mechanism.)

MR

XID

MX

The basicranial rods are forked at their distal extremities, where they bear a pair of maxillary rami (MR in fig. 5). These are hinged to them by a very efficient elbow-joint, enabling the rami to fold downwards, and so to protrude or retract the maxillæ which the rami support. It seems to me that these rami correspond to the cardo pieces of the maxillæ of other insects (as CA in fig. 6). The name "cardo" has been given (by Kirby) to what I term the labial rami (BL, fig. 5), which do not support the maxillæ and are scarcely represented in the ant (fig. 4). It is safer to designate all these structures by terms which do not involve a theory.

The modus operandi of the maxillæ on their rami is noteworthy. Each maxilla has a flat stipe surmounted by a lacinia resembling a knifeblade, and bearing (in the honey bee a rudimentary) palp at the waist. The blade can bend downwards and

An engineering friend on seeing this remarked, that it involved the principle of a machine lately patented for producing a limited and steady movement.

backwards on the stipe (see fig. 2) so as to be out of the way and to let the stipe project as a flat plate. When the suspensorium is retracted the two maxillæ are thus bent down, and their platelike stipes are approximated, furnishing a hard underlip for the mouth, upon which the mandibles play in their operations (as in cutting a piece of cork, or when the carpenter-bee operates on wood). The delicate limiting membrane which extends from the maxillary rami to the maxillæ is stretched when the suspensorium is protruded and thus serves to divaricate and fix the maxillæ.

The labial rami join the distal end of the maxillary rami with the labium, thus giving an additional joint, and a hinge which can move freely backward and forward, the result of which is great play to the parts of the labium. The labium consists of a basal piece, usually termed submentum, and of a middle piece, usually called mentum. It is safer to refer to these parts respectively as the basilabium and medilabium. The distilabium may indicate collectively the parts known as paraglossæ, labial palps, and ligule (PG, LF, and LG of figs. 4 and 5).

Many of the allies of the bee have these parts so simplified as to afford instructive hints as to their nature and relations. In Stizus grandis (with proboscis scarcely retractile) the basicranial rods are merely high ledges upon the margins of the excavated basicranium, and serving for insertion of the maxillæ. The ant (fig. 4) has only one basi-cranial rod, as if the two sides of the excavation had approximated and coalesced into a regular endodeme. Here the maxillary rami are nearly as in the bee, but the labial rami are almost obsolete, and the distalabial parts are much condensed.

The series of gradations thus presented gives promise of further discovery, and in attempting to correlate the parts of insects of different types I have fallen on some interesting revelations. It is at this part that Huxley's otherwise excellent description of the cockroach (Anatomy of the Invertebrated Animals, chap. vii,) is specially defective. He states that its endocranium "extends as a cruciform partition from the inner face of the lateral walls of the cranium to the sides of the occipital foramen," and adds that the centre of the cross is pierced by a rounded aperture through which the circumoesophageal nerve-collars pass. Fig. 6 will show how widely it differs from a cruciform pattern: and a comparison of this with figs. 3 and 4 will enable us to interpret its structure. Its lateral margins answer to the endocranial pillars of

the bee. Its anterior margin is the transverse ligament which usually binds together the roots of the mandibles, and prevents their divarication. These parts are webbed so as to form a flat (or broadly grooved plate) excepting at the centre where a passage is required for the nerves. In the Locust the lateral pillars approximate more closely so as to resemble the letter x, and so as to confirm the interpretation here offered. In describing the maxillary adjustments, Mr. Huxley seems to be still more unsuccessful. He states that the maxillary cardo is connected with "a thin band which runs round the posterior margin of the epicra'nium and is firmly united with it only on its dorsal side." Thus he regards the maxillæ as inserted

on the back of the skull through a band which he is consequently compelled to regard as a part of the cranial wall.

This view, if sustained, would clash with the mode of suspension observed in the bee, where the maxillæ have endocranial connections with the basi-occipital or ventral region of the skull. careful examination of the cock

A

X19

MX

roach has convinced us that here also the cardines of the maxillæ rest on a ridge which crosses the basis-cranii in front of the occipital foramen, and that it is only a slender ridge, not intimately connected with the maxillæ, which passes round like a rim behind this foramen. The transverse ridge which supports the maxillæ of the cockroach thus turns out to be only a simplified variation of the bee's suspensorium.

The basi-cranial region of coleoptera seems unwilling to be brought into line with the same part in other insect tribes: and Gegenbaur is certainly wrong in citing them as an instance of insects with large endocranium. The occipital foramen of beetles is arched over by a small but beautiful framework, which may correspond to Wolff's jugum at the root of the bee's mesocephalic pillars. In the beetles there are no pillars however, at least in the normal situation; but if we examine the clypeus we shall find the upper ends of such pillars, with ridges descending near the outer walls to the anterior basicranial region (to the submentum); and near their lower end the maxillary cardines are

inserted. This may indicate that the beetle has the usual parts, but resolved so as to give the long mentum, submentum, and gula, while other insects have all these parts condensed into the complex system of cross ridges in advance of the occipital foramen.

Only a few words can be said as to the cranial splachnodemes, or that part of the endocranium which consists of hardenings of the pharynx. The mouth is floored by a stiff, tongue-like plate (hypopharynx or lingua, to be distinguished from the long ligule or tip of the labial proboscis). This hypopharynx has a large number of small perforations which Wolff has shown to be olfactory it receives two large ducts from the cephalic salivary glands. From the posterior end of the hypopharynx run back two long rods, barbed on one side at their extremities. Over the mouth is a similar but simpler epipharynx. To these chitinous pieces the border of the pharynx is attached, and they are supplied with muscles. If we open the bee's mouth, we shall find the funnel-shaped opening kept expanded by the epipharynx above, the hypopharynx below, and its long processes (faucial processes we may say) at the sides. All these hard structures keep open the soft membrane of the pharynx, just as a naturalist's dredge is kept gaping by its iron armature. The piercing insects have the cranial splachnodemes developed into a strong pharynx-case which emits and supports the piercing setæ.

EXPLANATION OF CUTS.

FIG. 1.- Internal view of frontal region of bee. C, clypeus: E C, epicranium: G, gena: LR, labrum: M D, mandible: OC, compound eye: AT, insertion of antennæ. FIGS. 2. and 3.- Lateral and posterior (diagrammatic) views of head of bee. MC, mesocephalic pillars: BR, basicranial rods: MR, maxillary ramus: BL, basilabium: MD, mandible: MX, maxilla (its blade folded): A T, antenna: FO, occipital foramen.

FIG. 4.-MS, suspensorium of ant: MR, its maxillary rami: MX, maxillæ: BL, basilabium: ML, medilabium: PG, paraglossæ: LG, ligule: LP, labial palp: FO, occipital foramen: MC, mesocephalic pillars.

FIG. 5.-Bee's suspensorium and its connections. BR, its basicranial rods, arising from front of (FO) occipital foramen: M R, its maxillary rami, supporting (MX) maxillæ: (BL) basi labium: M L, etc., as in flg 4, maguifled 30 diameters. Below BL its labial rods are seen.

FIG. 6.- Endocranium, etc., of cockroach (Blatta). EC, endocranium: CA, cardo: MX, etc., as in fig. 4.

The thoracic salivary glands send their long duct to the medilabium and thence to the ligule. Carl v. Siebold has discovered three distinct salivary systems in the bee, two cephalic and one thoracic. (Zoologist, 1873, p. 3498.)

SUB-ELYTRAL AIR-PASSAGES IN COLEOPTERA. BY CARL F. GISSLer, of Brooklyn, N. Y.

THE rapidly progressing coloration of the entire integument at the time of transition from the chrysalis into the imago-state, the closing chapter in ontogenesis, is partly due to the photographic influence of light, partly to an oxidation by the atmosphere, produced by increased activity of breathing often observed in the first few minutes of existence as imago. By the fuller breathing and repeated extending of the wings and elytra (by lifting the latter, if connate), a heightened gas-exchange is made possible in the still semi-chitinized integument.

Another thing for us to consider in the elytron, now receiving the finishing touch, is its pattern and sculpture inherited from ancestors and often varied through climatological influences as well as through the law of adaptation and the phenomenon of mimicry. In many elytra we find fine pores on the upper side and in others longitudinal canals. I do not take the longitudinal canals of the uppermost layer, the cuticula, for tubes with walls proper, but regard them merely as lacunary clefts, the spaces through which air found access in the first few moments of existence as chrysalis solidifying and gluing together the elementary cells of the elytron.

In Opatrinus and Boletotherus we find a small elongate "plate" produced by a fold of the matrix; it is more (Opatrinus) or less. (Boletotherus) concave and occurs on the inner side of the epipleuræ, about in the middle where its thinnest margin is inflexed. This inflection is an arrangement for pleural breathing. The fold occurs especially in those species of Coleoptera where the epipleuræ are wanting, Buprestidæ, Curculionidæ, etc., and is called by Dr. Leconte "inflexed epipleural fold." He says its object is to enable the insect to fix the elytra and body firmly together.

In many, if not in all winged Coleoptera, we also find a small, more or less circular smooth niche, usually near the inner humeral bend of the elytron, undoubtedly intended for fitting into the wing and holding it in position. The inner fold may be called "plica trachealis," the niche (excavation) "fossa."

The plica, often running parallel with the external epipleura,