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Rh ECORPIOXS.] ARACHNIDA 285 From the above L. Dufour (I.e.} dissents. Accor.liug to his researches, which appear to have been pursued under the great advantage of having fresh as well as living examples to observe and dissect, the heart (or dorsal vessel) is not divided into chambers at ull ; its chambered appearance, which misled Newport and others, i rising from inevitable changes in the form of the organ after death, and long immersion iu spirit of wine. Dufour gives very exact figures and descriptions of those changes. According to him the heart is a simple, undivided vessel running throughout the whole body, only narrowing at the fore part of the caput, and in its passages through the tail ; and from this tube various lateral veins and arteries issue, those from the hinder or tail portion being pro fusely branched. He dissents entirely from Newport, lilanchard, and others, with regard to the mode above mentioned in which the vital fluid is conveyed to and from the pulmo-branchia?, but he con fesses that he has not been able to find out how it is actually effected, though he believes that the pulmo-branchial laminaj are permeated by vascular ramifications spread out over every one of their leaves, and that in these ramifications the fluid receives the benefit of the air admitted to the lamina?. Siebold, however, says that no traces of blood-vessels have been found in the pulmonary lamellae of another order, Araneidea; and it is hard to believe but that, if such details as those given by Newport in regard to the scorpion actually existed, Dufour, with the advantage of fresh examples to dissect, should have been unable to discover it. On the whole, it seems too soon, even yet, to dogmatise on the position of the scorpions from their respiratory and circulatory systems. That they have these two systems, the first by means of a dorsal vessel, with lateral branches, the latter by a kind of pouch containing a modification of trachea?, is certain ; and that their system is different from that of some other groups is also certain, but in the absence of a more perfect know ledge of the real nature of the difference, its true value cannot well be yet ascertained. Nervous System. A longitudinal row of nine according to Newport, eight ganglia, connected by a double nervous chord, is situated in the median line of the body, below the intestinal canal. The first ganglion consists of two lobes, the upper one of which, occupying a position some what analogous to that of the brain in the Vertebrata, is so called (cerveau) by Dufour. From these lobes the optic and other nerves issue, some of them being connected with the various parts of the mouth and the legs. A nervous collar, according to some authors, surrounds the oesophagus. Dufour, however, disputes the existence of this collar, and explains how the idea of it arose, I.e., pp. 556, 557. Of the remaining ganglia four are, according to Dufour, situated in the abdomen, and from these four there spring on each side and underneath, branching nerves, which run to each of the pulmo-branchiaj respectively and their adjacent parts, as well as to the viscera and tissues of the abdomen. The first abdominal ganglion is in close con nection with the large thoracic one, and is in some instances so little developed that Newport and others, overlooking it, derived the nerves running to the first pair of pulrno- branchice from the thoracic ganglion itself, and thence allowed but three to the abdomen. The caudal ganglia, four in number, do not correspond to the number of segments, which are five, or counting the terminal bulb, six. From each caudal ganglion two lateral nerves only issue, except from the last, whence there issue three pairs; the extra ones, running back, and branching out into the muscles of the poison bulb, doubtless add greatly to its sensibility and irritability. The Organs of Reproduction occupy, both externally and internally, a similar position in both sexes. The ex ternal aperture is duplex, situated between the first and second segments of the abdomen, in front of and, in a manner, between the comb-like appendages, and covered by an operculum. Internally those of the male consist of a duplex set of vessels for the elaboration, collection, and conveyance of the seminal fluid to the external orifices, each orifice having its own set. The vessels, answering to testes, in which the seminal fluid is secreted, consist each of a tube forming three large quadrilateral, flexuose, and free, anastomosing meshes placed longitudinally ; those of one set sometimes coramunicating with the other at the lower mesh by a short, strong connecting tube. According to Treviranus the three meshes on either side anastomose with each other, having, in fact, a common connection throughout, but this L. Dufour considers to be an abnor mal case ; the vessels for the collection of the seminal fluid, vesiculcG seminales, are three for each set, and all open into the channel of emission ; this is produced backwards in the form of a long, fusiform, sheath-like channel, lying along the flanks of the abdominal cavity, and attenuated at both extremities ; within this channel is another slender, corneous sheath-like organ, prolonged to the genital aper ture, where it is exceedingly fine. This is &quot; le fourreau et 1 armure de la verge&quot; (Dufour), and within it is the intromittent organ itself, having a whitish cartilaginous, thread-like appearance. No recorded observations have yet decided the mode in which these parts of generation are used : the Scorpionides being nocturnal in their habits makes such observations very difficult, but all analogy is in favour of copulation by the exsertion and introduction of the thread-like organs above described into the female parts of generation. These consist of two ovaria, each composed of a membranous tube, fonning four large quadrilateral meshes in a longitudinal line on each side, anastomosing with each other and with those of the other side ; each of these ovaria ends in a simple oviduct (sometimes with, sometimes Avithout ovisacs) leading to the vulva or exter nal orifice. The general similarity of these female organs with those of the male is at once apparent. A curious point noticeable in these parts in the Scorpionides is their duplex character, and hence the question as to their mode of operation becomes of greater interest. It is remarkable that the only other Arachnids in which an intromittent organ is as yet known are among the Phalangides, a group widely separated from the Scorpionides in other characteristic details, though approaching much nearer to the pseudo- scorpions. Scorpions are ovo-viviparous, and, according to Dufour (I.e.), their period of gestation is of great length, extending even to fifteen or sixteen months ; but for five of these months, which occur in the winter season, Dufour concludes, from frequent observations, that the whole genital apparatus is, like the animal itself, in a dormant state, and that therefore no progress in the development of the ova takes place during this period. On the very important branch of this subject the embryology of the scorjrion reference only can be made to the works of Ileinrich Kathke, Reisebemcrkungen atis Taurien (contained also in Burdach s Physiology, Bd. ii. p. 242, et seq.) and to that of Dr Elias Metschnikoff, &quot; Embryologie des Scorpions,&quot; Z. Wiss. Zool., Bd. xxi. pp. 204-232, taf. xiv.-xvii. ; also sepa rate, Leipzig, 1870. GENERAL OBSERVATIONS. The sub-order Scorpiones forms a remarkably homogeneous group. It has been divided, however, into several families by Koch (Die Aruchn.) ; and various genera, based principally on the num ber and distribution of the eyes, the form of the fore margin of the cephalo-thorax, and the structure of the comb-like appendages attached to the under side of the abdomen, have been characterised. The species are tolerably numerousy but the whole group greatly needs revision, both in respect to its family and generic divisions, as well as in regard to the identification and determination of the species. Those found in Europe are of comparatively small dimensions, and are confined to the southern parts of the Continent ; the majority are tropical, attaining their greatest size nine or ten inches in length in Central Africa and South America. They are nocturnal in their habits, living by day underneath stones, behind the loose bark of trees, among the ruins and debris of old walls and buildings, and preying upon insects and other Arachnida ; they are said to be very partial to the eggs of spiders and insects. It