April 3, 1890] 



NA TURE 



525 



(12) Although physiological selection must in all cases refer 

 primarily to first crosses, its activity as a cause of segregation is 

 intensified in cases where it extends also to second ciosses. 



SCIENTIFIC SERIALS. 



American Journal of Mathematics, vol. xii., No. 3 (Balti- 

 more, March 1890.) — A memoir " Sur les equations aux dcrivees 

 partielles de la physique mathematique," by that brilliant 

 mathematician, M. Poincare, occupies pp. 211 294. Some idea 

 of the writer's aim will be gained from the following passages :— - 

 *'(}uand on envisage les divers pr jbiomes de calcul integral qui 

 se posent naturellement lorsqu'on vent approfondir les parties 

 les plus diffc-rentes de la physique, il est impossible de n'ctre pas 

 frappc des analogies que tous ces problcmes prcsentent entre 

 eux." " Cette revue rapide des diverses parties de la physique 

 mathematique nous aconvaincus que tous ces problcmes, maljjre 

 I'extreme varietc des conditions aux limites, et mcme des equa- 

 tions difforentielles, ont, pour ainsi dire, un certain air de famille 

 qu'il est impossible de meconnaitre. On doit done s'attendre a 

 leur trouver un tres grand nombre de proprietcs communes." 

 The concluding sentence is : " Je pourrai dire alors que les con- 

 clusions sont dcmontrees d'une fac^ on rigoureuse au point de vue 

 physique. Peut ctre mcme est-il permis d'espt'rer que, par une 

 sorte de passage a la limite, on pourra fonder sur ces principes 

 une demonstration rigoureuse meme au point de vue analytique." 

 ■ — The remaining article of the number is one on singular 

 sblutions of ordinary differential equations, by 11. B. Fine (pp. 

 295-322). Following the lead of Briotand Bouquet, this memoir 

 bases the theory of singular solutions on the differential equa- 

 tion, and avoids all use, direct or indirect, of the notion of the 

 complete primitive. 



In Jhilletin No. 2 of the Brussels Academy of Science, 

 M. E. Ronkar criticizes a paper by M, J. Liagre, on the mutual 

 impulse of the earth's surface and centre because of interior 

 friction. The paper in question dealt with the interior structure 

 of the earth, and the conclusions drawn have some bearing on 

 diurnal nutation. — In a paper on the venous pulse. M. l.eon 

 Fredericq gives his investigations into the form of various pulses 

 — ^jugular, venous, and carotid ; traces the identity of the pulse of 

 the jugular vein and that of the right auricle ; and discusses 

 generally the phenomena of circulation and respiration. The 

 same author adds a note on the preservation of oxyhemoglobin. 

 — M. A. F. Renard has examined phillipsite crystals from the 

 deposits obtained from the centre of the Pacific Ocean. These 

 microscopical crystals were discovered by Mr. Murray, and a 

 brief description of them published by him in conjunction with 

 the author in 1884 (Royal Society of Edinburgh). A more par- 

 ticular description and determination of the character of these 

 zeolites, and the deposits in which they occur, is now given. A 

 plate containing four drawings of the crystals accompanies the 

 paper. — M. G. van der Mensbrugghe, in a paper on the con- 

 densation of water-vapour in capillary spaces, reviews the 

 principal facts owing their origin to such condensation, and 

 shows that they are in confirmation of the theory propounded 

 by Sir William Thomson in 1874, in a paper on the equilibrium 

 of vapour at a curved surface of liquid. The experimental 

 verification of the formula there given will form the subject of 

 a second communication. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, February 20. — " Some Stages in the Deve- 

 lopment of the Brain of Clupea hareiigi/s." By Ernest W. 

 L. Holt, Marine Laboratory, St. Andrews. Communicated by 

 Prof. Mcintosh, F.R.S. 



The stages described are (i) newly-hatched or early larval ; 

 (ii) early post-larval ; (iii) h inch long ; (iv) i,' inch long. 



The development of the pineal region is treated separately, 

 and in this a fifth stage — ij\ inch long— is introduced. 



In the early larval stage the downward flexure of the fore part 

 of the brain is very noticeable. It appears due to the general 

 conformation of the head at this stage. A diverticulum of the 

 3rd ventricle extends downwards and backwards, its distal ex- 

 tremity underlying the optic commissure. The broad ventral 



commissure of the infundibulum, noticed by Mcintosh and 

 Prince in Anarr/iicas, is well marked. A commissure shuts oft 

 the lumen of the infundibulum from the hind part of the 3rd 

 ventricle immediately in front of the splitting off of the infundi- 

 bulum. The valvula appears in transverse section as a pair of 

 ridges externally to the tori, before it shuts off the aqueduct of 

 Sylvius. The cerebellar fold is very short. 



In the early post-larval stage "an apparent rectification of the 

 cranial axis' has taken place, by the upward rotation of the 

 cerebrum on its posterior end, doubtless owing to the rapid 

 development of the oral and trabecular cartilages, and con- 

 sequent forward rotation of the mouth. The same causes have 

 also operated so as to withdraw the diverticulum of the 3rd ven- 

 tricle from its position below the optic commissure. The infundi- 

 bulum has undergone vertical flattening. The future lobi inferiores 

 are indicated as lateral expansions, behind which the 3rd oculo- 

 nnotor nerves pass outwards from the centre of the ventral surface 

 of the cerebral mass. The infundibulum extends some way back 

 above the notochord as a thin-walled sac. Its walls are little 

 plicated compared with those in some other forms, e.g. , Rhombus, 

 Anarrhicas. 



In the iinch stage the olfactory lobes appear as bulbous masses 

 projecting from the front end of the cerebrum. A pale median 

 septum appears between the anterior extremities of the lateral 

 optic ventricles, its base resting on the fibrous tract over the hind 

 part of the 3rd" ventricle. The tip of the valvula now appears 

 in transverse section before its connection with the cerebral mass 

 can be made out, having thus grown forward. The cerebellum 

 has greatly increased in size ; instead of terminating as before on 

 the surface of the brain, it is now continued into a thick fold 

 bent sharply down on the anterior portion ; its posterior end 

 passes at once into the thin roof of the 4th ventricle. Two 

 fibrous bands cross over the aqueduct of Sylvius in the substance 

 of the cerebellum ; their lateral extremities are fused. The lobi 

 inferiores are better marked than in earlier stages. Longitudinal 

 bands of fibres pass back from the roots of the oculomotor nerves 

 through the medulla oblongata. Groups of large ganglionic cells 

 appear on either side of these bands, and are connected by a fine 

 commissure passing through both bands. At the origin of the 

 8th auditory nerves, this commissure is replaced by a St. 

 Andrew's cross of fibres, the dorsal limbs of the cross passing to 

 the nerve roots, and the ventral to the ganglionic areas. 



In the ij-inch stage the olfactory lobes are more elongated. 

 The olfactory nerves pass outwards from their anterior extremi- 

 ties. The septum behind the pineal body, after losing its ventral 

 connection with the fibrous tract over the 3rd ventricle, persists 

 for some way back as a cellular leaf-like appendage of the thin 

 median roof of the optic ventricle ; a few fibres pass back into 

 this appendage. 



Large ganglionic cells appear in the tori semicirculares about 

 the region of the splitting off of the infundibulum. 



From behind the region of the auditory nerves a ganglionic 

 area on either side persists backwards through the medulla 

 oblongata. 



Pineal Region. 



The roof of the thalamencephalon in the early stages is a 

 single layer of large columnar cells passing forward from the 

 front wall of the pineal stalk. It passes into the roof of the 

 cerebrum, the cells diminishing greatly in size. The superior 

 commissure of Osborn is present from the early post-larval stage ; 

 it it also present in the larval and post-larval Zoarces viviparnsy 

 where it is distinctly double. The first signs of the infrapineal 

 recess of Hoffman are seen in the Vinch stage. It is thus much 

 later in developing than in Sahno, and the fold forming its front 

 wall never extends backwards to the same degree as in that form 

 and in Anarrhicas . This fold, in the post-larval Zoarces, is 

 thickened in its apex, and lodges a fine commissure. As pointed 

 out by Balfour in Elasmobranchs the fold is due to the upward 

 rotation of the cerebrum. 



The fibrous tract over the 3rd ventricle in the herring is well 

 marked in the 4-inch stage. It is seen to consist of fibres passing 

 upwards and inwards from the optic thalami to the middle line 

 above the 3rd ventricle, and then running forward to the stalk of 

 the pineal body. 'Jhe tract has a double nature, as is readily 

 seen in vertical longitudinal sections of a herring i^'._, inch long. 

 It is seen here to be a backwardly directed fold of the brain roof,, 

 continuous ventrally with the back wall of the pineal stalk, and 

 dorsally with the roof of the optic ventricle, the apex of the fold 

 being the posterior commissure. Its length in this form is due 

 to the flattening of the brain, the tract being very s'^.ort in 



