8 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Origin of the Optic Nerve.* — J. Manouelian comes to the following 

 conclusions on this subject. The optic nerve has two origins, a peri- 

 pheral and a central. The peripheral origin resides in the ganglionic 

 cells of the retina. The protoplasmic ramifications of these cells unite 

 with those of the internal prolongations of the bipolar cells whose peri- 

 pheral prolongations connect the rods and cones. Luminous impressions 

 received by the cones and rods transmit to ganglion cells, whose cylin- 

 draxial prolongations conduct to the mesencephalic centres. These 

 cylinder-axes are the centripetal fibres of the optic nerve. These fibres 

 give out into mesencephalic centres terminal arborisations connecting 

 on one side with nerve-cells whose axes go to the higher centres, on the 

 other side with the neurons with peripheral axes, and these neurons 

 constitute the central origin of the optic nerve. This means that the 

 cylindraxial prolongations of the cells become fibres of the nerve. 



Tooth-Band in Toad.f — R. Oeder has succeeded in finding a tooth- 

 band in the maxilla of the toad. By the time the tail of the tadpole 

 has disappeared there is no trace of this vestigial relic. 



Nasal Fossa of Vertebrates.^ — L. Dieulafe reviews in an exhaustive 

 manner the morphology and embryology of the nasal fossa from Amphi- 

 oxus to man, including personal observations on all the groups. One 

 point may be quoted, viz. the appearance of Jacobson's organ in Mammals. 

 It arises very early (in sheep of 10 mm., moles of 6 mm.) : it is a groove 

 which soon becomes closed to form a cylindrical tube (in sheep 14 mm.) 

 over a considerable part of its length. Towards the anterior extremity 

 a part persists (Stenson's canal) and forms a communication with the 

 buccal cavity. Under the septal cartilage this organ is in connection 

 with the cartilage of Huschke or Jacobson. In the human embryo of 

 19 mm. this organ is placed above the inferior edge of the septal carti- 

 lage apart from the cartilage of Huschke. Gegenbaur regarded it as 

 the exhalent duct of a septal gland. In the majority of Mammals 

 Jacobson's organ develops and maintains its relations, but in bats and 

 in man it disappears. 



Human Skull without Intermaxillary.§ — A. Fischel describes a 

 skull in which the intermaxillary (or premaxillary) is either quite absent, 

 or present simply as the merest vestige, and in which the incisors are 

 absent. It is interesting to find that the maxillary processes of the first 

 visceral arch have grown further forward than usual, sharing in forming 

 the foramen incisivum which the intermaxillary normally surrounds, 

 and largely concealing the defect — an instance of what is called a 

 " regulation-process." 



Pectoral Skeleton of Teleosteans.|| — H. H. Swinnerton has investi- 

 gated the development of the pectoral skeleton in the salmon and stickle- 

 back by means of reconstruction in wax from serial sections. The earlier 

 stages in the two forms are fundamentally the same. The mesocoracoid 



* Journ. de l'Anat. et Phys., xli. (1905) pp. 458-77 (1 pi.). 



t Zool. Anzeig., xxix. (1905) pp, 536-8. 



% Journ de l'Anat. et Phys., xli. (1905) pp. 300-18, 478-560. 



§ Anat. Anzeig., xxvii. (1905) pp. 561-75 (7 figs ). 



|| Quart. Journ. Micr. Sci., xlix. (1905) pp. 363-81 (1 pi. and 3 figs.). 



