33° 



NA TURE 



\J*yi- 



Brachiopods, though every argument on which their former 

 connection was based is demonstrably false. 



But to a great extent the whole matter turns upon our concep- 

 tion of segmentation, a subject which Mr. Sedgwick's recent 

 speculations (Q. J. M. S., No. xciii. 1884) may very seriously 

 modify. Sedgwick derives all metameric segmentation from a 

 Ccelenterate-like ancestor, with a. pouched gut like that of all the 

 Actinozoa. The blastopore, including both mouth and anus, is 

 derived from the Aclinozoan mouth, the double nerve-cord from 

 the aggregation of the nervous system round the mouth of the 

 polyp, and the nephridia from specialised parts of the pouches 

 represented now by the circular canal of Medusae or the mesen- 

 teric perforations of Actinozoa and the pores leading to the ex- 

 terior in those forms from the mesenteric chambers. But 

 it is impossible to discuss this theory fully ; it is enough to 

 point out that it postulates segmented ancestors of all animals 

 above Ccelenterates. Mollusks, Brachiopods, and Sagitta must 

 according to it have been once segmented, just like Vertebrates, 

 Arthropods, and Worms. But surely this is a violent assump- 

 tion. There is no evidence of segmentation among Mollusks 

 save in Nautilus, for even the pedal commissures of Chiton in no 

 way indicate a truly segmented condition ; nor any among 

 Polyzoa or Brachiopods save the four nephridia of Rhynchonella. 

 And it is by no means clear that the development of Sagitta 

 indicates its descent from an ancestor with " three pairs of gut- 

 pouches." The vast number of animals with a single pair of 

 nephridia can scarcely all be derived from ancestors with many 

 pairs ; and Hatschek's description of the origin of segmented 

 nephridia (in Polygordius) from a single pair seems far from 

 supporting Sedgwick's view. The still insufficiently im 

 excretory organs of Rhynchonella, and the four gills, &c, "1 

 Nautilus, seem not enough to indicate descent of the groups to 

 which these forms belong from segmented ancestors. On the 

 contrary, it seems far more likely that the types we have more 

 particularly discussed are all derived from some unsegmenteA 

 trochosphere ; and that the segmentation of the Chretopods 

 only became marked after the ancestor of the Phoronis type had 

 severed his course from the common stock of Worms. The dis- 

 tinction of segmentation and non-segmentation would thus divide 

 the Invertebr.n 1. 



As regards the Gephyrea, there is much reason for connecting 

 such members of the group as Sipunculus, Phascolosoma, and 

 Bonellia with the unsegmented Phoronis type. But Hatschek 

 maintains that the development of Ecbiurus proves it to be a de- 

 generate Chsetopod ; and if so, Caldwell (toe. fit.) is ready to 

 admit that the others may be further stages in such degeneration. 

 But even as regards Echiurus this degeneration is far from clear. 

 The Platyelminths seem also never to have been segmented, 

 and their "water-vascular canals" may give us some indication 

 of the organs from which are derived the nephridia of Phoronis, 

 Gephyrea, Brachiopods, and Mollusks. The larva of Thysano- 

 zoon has many points in common with the trochosphere, thovgh 

 its want of an anus is strange and difficult to explain. The 

 Rotifers are acknowledged to be persistent trochospheres. And 

 accordingly all these forms may be older and more primitive, by 

 virtue of their lack of segmentation, than all the Chsetopod . 



D. W. T. 



SCIENTIFIC SERIALS 



The Journal of Anatomy and Physiol gy, January 1SS4, 

 contains : — A. Milnes Marshall, M.D., certain abnormal con- 

 ditions of the reproductive organs of the frog.- — S. A. Wad- 

 dell, M.B., the urea elimination under the use of potassium 

 fluoride in health. — B. C. A. Windle, M.A., M.D., primary 

 sarcoma of the kidney. — R. J. Anderson, M.D., transverse 

 ments of human ribs. — Arthur W. Hare, M.B., a 

 method of determining the position of the fissure of Rolando 

 and some other cerebral fissures in the living subject. — G. 

 Hoggan, M.B. , new forms of nerve terminations in mam- 

 malian skin. — J. Symington, M.B., the fold of the nates. — W. 

 Ainslie Holies, M.D., researches into the histology of the 

 central gray substance of the spinal cord and medulla oblongata. 

 — D. J. Cunningham, M.D., the musculus sternalis. — C. W. 

 Cathcart, M.B., movements of the shoulder-girdle involved in 

 those of the arm on the trunk. — J. B. Sutton, the relation of the 

 orbito-sphenoid to the region pterion in the side wall of the 

 skull. — Anatomical notices. 



April contains : — J, B. Sutton, the nature of certain ligaments. — 

 F. LeGros Clark, F.R.S., some remarks on nervous exhaustion, 



and on vasomotor action. — C. B. Lock wood, F. R.C.S. Lond., the 

 development of the great omentum and the transverse mesocolon. 

 — Arthur Thomson, M.B., notes of two instances of abnormality 

 in the course and distribution of the radial artery. — Js. W. 

 Barrett, M.B., the cause of the first sound of the heart, and the 

 mode of action of the cardiac muscle. — Prof. Cleland, F.R.S., 

 notes on raising the arm. — R. W. Shufeldt, M.D., osteology of 

 Ceryle alcyon. — A. M. Patterson, M.B., notes on abnormalities, 

 with special reference to the vertebral arteries. — Geo. Hoggan, 

 M.B., on multiple lymphatic na;vi of the skin, and their relation 

 to 'im kindred diseases of the lymphatics. — Prof. Cleland, 

 F.R. S., notes on the viscera of the porpoise and white-beaked 

 dolphin. — W. Arbuthnot Lane, F.R.C.S., coslal and sternal 

 asymmetry. — Anatomical notices. 



The Journal of Physiology, vol. v. No. I, contains : — E. 

 Klein, M.I>., F.R.S., the bacteria of swine-plague. — T.Lauder 

 Brunton, on the rhythmic contraction of the capillaries in man, 

 and on the physiological action of condurango. — J. Blake, on 

 the connection between physiological action and chemical con- 

 stitution. — II. H. Donaldson, and L. T. Stevens, note on the 

 action of digitalis. — W. H. Gaskell, on the augmentator (acce- 

 lerator) nerves of the heart of cold-blooded animals. 



Archives Italiennes do Biologic, tome iv. fasc 3, contains:— 

 B. Grassi, the development of the vertebral column in bony 

 fish. — L. Luciani, on the mechanical stimulation of the senso- 

 motory centres of the brain-cortex. — A. Moriggia, on a new 

 method of isolating the sensibility of the mobility of the 

 nerves. — G. Magini, the induced unipolar current and the 

 stimulation of nerves. — F. Marino-Zuco, upon the | 

 with regard to toxicological investigations. — S. Richiardi, 

 on the distribution of the nerves in the follicle of the tactile 

 hairs of the ox, which are provided with a vascular erectile 

 apparatus. — Ph. Lussana : (1) on the brain of the boa: 

 considerations on comparative neuro-physiology ; (2) on the 

 sensibility of parts uncovered by skin; (3) on colour-hearing. 

 — A. Marcacci, the areola-mammillary muscle. — P. Foa, con- 

 tribution to the study of the physiopathology of the spleen. 

 — L. Griffini and G. Tizzoni, experimental study of the partial 

 reproduction of the spleen ; novel researches into the total re- 

 production of the spleen : an experimental contribution to the 

 hematopoetic function of the connective tissue. — J. Bizzozero and 

 A. A. Torre, upon the origin of red blood-corpuscles in the 

 various orders of the Vertebrata. — J. Cattaneo, fixation, staining, 

 and preservation of Infusoria. 



Tome v. fasc. 1 contains : — C. Giacomini, the fascia dentata of 

 the hippocampus major in the human brain. — A. Borzi, new 

 studies in the sexuality of Ascomycetes (preliminary note). — L. 

 Solera, contribution to the physiology of the succus intestinalis. 

 — F. Selmi, tolerance of arsenic in domestic animals, and its 

 distribution in the organism. — Ph. Lussana, on the quantitative 

 and qualitative secretion of bile in the state of inanition after the 

 section of the two pneumo-gastric nerves. — L. Camerano, (1) on 

 the development of the Amphibia, and on what has been called 

 their "Neotenia" ; (2) researches on the prolongation of the bran- 

 chial periods of the Amphibia. — G. Romiti, anatomical investiga- 

 tion of a case of death from the bite of a viper. — P. Fanzago, on 

 the nest of Geophilus flavus. — E. Levier, the origin of the tulips 

 of Savoy and of Italy. — P. Albertoni, critical and experimental 

 studies upon the action and metamorphosis of certain substances 

 in the organism, with respect to the pathogenesis of acetonemia 

 and diabetes. — L. Griffini, (1) an experimental study of the 

 partial regeneration of the liver (preliminary communication) ; 

 (2) on the total and partial reproduction of the follicular appa- 

 ratus and of the calyciform papillae in the rabbit (preliminary 

 communication). — M. H. Peracca and C. Deregibus, note on 

 Ccelopeltis insignitus. — L. Vincenzi, histological note on the true 

 origin of some cerebral nerves. — A. Mosso, employment of the 

 balance in the study of the circulation in man. 



SOCIETIES AND ACADEMIES 

 Edinburgh 

 Mineralogical Society, June 24. — This meeting was held at 

 the Museum of Science and Art, Edinburgh. — Prof. Jas. Geikie, 

 F.R.S., in the chair. — The following papers were read : — On forms 

 of silica, by Prof. John Ruskin, D.C.L. The Chairman and 

 Dr. Dudgeon made some remarks. — On the application of the 

 periodical law to mineralogy, by Prof. Thos. Carnelley of Dundee. 

 — On the origin of the Andalusite schists of Aberdeenshire, by 



