Feb. 4. 1886] 



NATURE 



IIZ 



tending to show that in the Baltic the tides rise higher in summer 

 than in winter, the author is disposed to attribute the phenomenon 

 rather to local physical causes than to Baeyer's astronomic theory 

 of solar action. — Note on the geological formation of the Juan 

 P'ernandez islands, by A. L. Renard. The prevailing 'rocks 

 throughout this group would appear to be mainly basaltic, with 

 little or no trace of lavas or other recent eru|.itive mattei-. — On 

 some new groups of fossil remains from the Upper Chalk and 

 Lower Eocene I'ertiary formations of Belgium, by Ed. Dupont. 

 These specimens, now mounted in the lirussels Museum of 

 Natural History, include fragments of a Dinosaurian [Orthoinerus 

 dolloi) from the Maestricht district ; the head and various bones 

 of the gigantic Alosasaurus campcri^ from Limbourg and Mon- 

 tague Sainte- Pierre ; remains of a new type of Klosasaurian 

 recently described by M. Dollo under the name of Pliopladcarpus 

 marshi, from Maestricht ; remains of another Mosasaurian from 

 Ciply, new in Europe, but well known in America, which M. 

 Dollo has named Poly^^onodon ciplycnsis ; the carapaces of two 

 large turtles from Maestricht, Chelonia hoffmanni. Gray, and Ch. 

 suyderbuycki, Ubags ; lastly, the skull of a crocodile afiSliated 

 by Dollo to the Crocodihis affinis discovered by Marsh in the 

 Eocene of the far west. — Note on the whale captured last May 

 off Fecamp, by P. J. van.Beneden. At first supposed to be a 

 Balatioptera musciilus, L., or else a new species, the authoi 

 shows that this cetacean is the Baliiiioptera rostrata, Fabricius, a 

 specimen of which was taken in 1878 near Villefranche in the 

 Mediterranean. — A study of Fran9ois Huet and his philosophic 

 writings, by O. Merten. 



SOCIETIES AND ACADEMIES 



London 



Royal Society, January 7. — " Contributions to the Anatomy 

 of the Central Nervous System of the Plagiostomata. " By 

 Alfred Sanders, M.R.C.S., F.L.S. Communicated by Dr. 

 Gunther, F.R.S. (Abstract.) 



After referring to the literature of the subject, and describing 

 the macroscopic aspect of the brain, and partly the distribution 

 of the cranial nerves, the author proceeds to give an account 

 of the histology of the segments of the brain. 



The olfactory lobes are well developed. They present three 

 layers. Internally cells of the smallest category are found ; they 

 give off several processes which join a network penetrating the 

 whole layer ; through the medium of this netsvork these cells 

 communicate with the glomeruli which form the middle layer. 

 These glomeruli are much better developed than in the Teleostei ; 

 here they present a central core of closely intertwined fibrillfe 

 inclosed externally by fibrils of a larger size, in the course of 

 which cells are developed ; these are arranged parallel to the 

 long axes of the glomeruli, and join the external layer, which 

 consists of fibres passing from the anterior end of the olfactory 

 lobe to supply the olfactory organ. 



In the Rays these lobes are solid, but in the Scyllium, Rhina, 

 and Acanthias they contain a ventricle which communicates 

 through a long peduncle with the ventricles of the cerebrum. 



The cerebrum presents externally a layer of neuroglia without 

 cells, or at least with comparatively few ; the remainder of the 

 parenchyma presents cells of a medium size which are usually 

 distributed in groups with neuroglia interspersed between them ; 

 these groups in Scyllium contain from nine to fifteen cells, in the 

 Rays generally more. Four special groups of cells occur towards 

 the base of the brain, two in the outer and two in the inner 

 walls ; from the former arise the anterior commissure, and from 

 the latter the crura cerebri. 



Two ventricles occur in the cerebrum of Scyllium, Rhina, and 

 Acanthias which homologise with the lateral ventricles in the 

 cerebrum of Mammalia. At the posterior part they coalesce 

 into one chamber which is in communication with the third 

 ventricle ; this chamber is evidently the foramen of Monro. Dr. 

 Wilder is of opinion that the ventricles of the olfactory lobes 

 represent the lateral ventricles, and that their apertures of com- 

 munication with the above-mentioned chambers homologise 

 with the foramina Monroi. A consideration of the case renders 

 this idea improbable. In the Rays the ventricles are reduced 

 to a very small chamber occupymg the posterior end of the 

 cerebrum. 



The crura cerebri form two projecting walls of a gutter- 

 shaped passage which communicates with the third ventricle. 

 As Prof Owen has already pointed out, they probably homo- 

 logise with the nervous cords which connect the supra- with the 



infra-cesophageal ganglia in Invertebrata ; and it is through the 

 third ventricle that the oesophagus of the probable invertebrate 

 ancestor of the Vertebrata could have reached the present dorsal 

 surface without breaking through nervous tissue ; for dorsally 

 the choroid plexus and pineal gland cover in this ventricle, there 

 being no nervous tissue here, and inferiorly it communicates 

 through a chamber in the hypoarium with a chamber in the 

 centre of the pituitary body ; the endothelium lining the former 

 being continuous with the endothelium lining of the latter. 



The optic lobe which arches over the aqueduct of Sylvius 

 corresponds to the tectum lobi optici of the Teleostei ; the structure 

 is much simpler, although comparatively speaking the lobe is 

 larger. Externally it is occupied by the fibres of origin of the 

 optic nerve ; within these a transverse commissure is visible 

 homologising with the transverse commissure in the tectum lobi 

 optici of Teleostei. Internally a ganglion of large cells occurs 

 variously arranged in the different species ; these cells are of 

 large size, but differ from the cells of the ventral horn of grey 

 matter of the cord in texture, and in the fact of giving off only 

 one process as a rule, which process runs into the above-men- 

 tioned transverse commissure. Numerous cells of small size, 

 many of which are fusiform, occur in this lobe ; these are more 

 numerous in the centre. 



The author's researches do not bear out the statement of Rohon 

 that the thalamencephalon projects backward and covers the 

 mesencephalon in the optic lobe ; so that according to this author 

 it is composed of both these segments of the brain. Apart 

 from embryological considerations, which give no countenance 

 to this idea, there is nothing in the structure of this lobe which 

 indicates an origin from two distinct primary vesicles of the 

 brain ; on the contrary, its structure is homogeneous. 



The cerebellum presents a structure corresponding to that in 

 the Teleostei. There are, counting from within outward, the 

 granular, fibrous, Purkinje cells, and molecular layers. The 

 differences consist in the greater number of processes given oft 

 by the Purkinje cells, and in the greater number of small cells 

 found in the molecular layer. Another difference is found in 

 the presence of a ventricle which is largest in Rhina, Acanthias, 

 and Scyllium, and reduced to very small dimensions in the Raja. 

 The molecular layer is continued down on to the surface of 

 the medulla oblongata from the cerebellum, forming the restiform 

 bodies. In the spinal cord there are distinguishable three 

 columns on each side : a dorsal above the dorsal cornu, a lateral 

 at the side, and a ventral beneath ; the latter consists of fibres 

 of a larger calibre than those constituting the other columns, 

 but no gigantic fibres — the so-called Mauthner's fibres — are 

 present, as in the Teleo-tei. 



The deep origins of the cranial nerves. The optic nerve 

 arises as above-mentioned from the outer half or more of the 

 optic lobes, also by a few fibres from the hypoarium. This 

 fact was contradicted by Bellonci in reference to the origin of this 

 nerve in Teleostei, but further researches and consideration 

 compel the author to adhere to his original statement. 



The oculomotor arises from a ganglion in the floor of the 

 aqueduct of Sylvius. There is no decussation of the fibres of origin 

 of this nerve as is stated by some authors ; the error probably 

 arose from the presence in this region of a decussation of fibres 

 derived from the transverse commissure in the optic lobe : this 

 decussation of fibres corresponds to the commissura ansulata in 

 Teleostei. 



The facial arises from a small bundle of fibres which comes 

 forward from the lateral columns of the cord, and is situated 

 at the side of and slightly above the central canal. 



The trifacial arises from a tuberosity overhanging the fourth 

 ventricle immediately contiguous to the restiform bodies, also 

 from the grey matter of the floor of that ventricle. 



The vagus arises from a series of rounded tubercles which 

 occupy the lateral portions of the floor of the fourth ventricle. 



Linnean Society, January 21. — W. Carruthers, F.R.S. , 

 Vice-President, in the chair. — Mr. Harry Veitch exhibited, in 

 illustration of Dr. Masters's paper, a series of living conifers, 

 among which were : Abies Forlunci, A. nobilis, A. graiidis, and 

 A. amabilis ; also Pseitdolaryx KiVmpferi^ Piced Oinorika^ Pinus 

 Pencei, Arthrotaxis selaginoides, and others. — Mr. E. M. Holmes 

 exhibited a specimen of the ergot of Diss {Aruiido teiiax) from 

 Algeria. This ergot is said to be more active medicinally than 

 that of Rye, and is slenderer and twice or thrice its length, and is 

 attributable to the fungus Claviccps purpurej.. — Dr. C. Cogswell 

 drew attention to dried specimens of the species of maples \^Accr) 

 of Canada collected by him in Nova Scotia, and of Sisy- 



