444 SUMMARY OF CURRENT RESEARCHES RELATING TO 



roundish diverticulum two days after the fish is hatched. It grows 

 quickly and tills with air which is swallowed at the surface. It becomes 

 spherical and is inclosed in a firm envelope. As the pressure increases 

 a part of the bladder is protruded like a hernia. This grows quickly and 

 becomes the anterior part of the hour-glass-shaped air-bladder. The 

 shape gives the bladder relatively more strength to resist pressure, and 

 it may be an advantage to have two bladders in a line instead of one 

 large one. 



Gestation in Acanthias vulgaris.* — L. Blaizot finds that in this 

 dogfish there is no nutriment provided by a secretion or degeneration of 

 the uterine wall, and that the embryos are not bound to the uterine wall 

 by their vitelline vesicle. It may be said that Acanthias is intermediate 

 between the oviparous dogfishes, and those with pronounced viviparous 

 adaptations. 



b. Histology. 



Nervous Elements in Fishes.f — A. Nemiloff has studied the 

 nerve-cells of the cerebral, spinal, and sympathetic ganglia, and dis- 

 cusses the minute cytoplasmic and nuclear structure, the structure of 

 the surrounding envelopes, the " trophocytes " between the cell and its 

 envelope, the interstitial tissue (including a small bundle of striped 

 muscle in the ganglion of the vagus in Lota vulgaris), the inclosures 

 and parasites, and the changes in the nucleus. 



Ventricular Fibre of Brain of Myxinoids.J — Howard Ayers 

 describes a fibre within the ventricular cavity of the brain of Bdello- 

 stoma and Myxine, which serves to connect the ependyma cells of the 

 cavity and of the spinal canal. The fibre for the most part follows the 

 outlines of the ventral portion of each chamber, but it is much coiled in 

 the fourth ventricle. It consists of innumerable fibrils derived from the 

 ependyma cells, lying in the cavity of the brain and spinal cord. It is 

 certainly an organ of relation, bringing all parts of the ventricular cavity 

 into intimate communication. It may be connected with the vaso-motor 

 control of the ventricular lymph supply. 



Epidermal Sensory Cells in AmphioxusJ — H. Joseph corroborates 

 the occurrence of true sense-cells among the epidermic cells of the lance- 

 let, and gives some details in regard to their (variable) distribution and 

 minute structure. 



Histogenesis of Nervous System. || — Oskar Schulze describes a 

 number of observations on a large variety of animals, which contradict 

 the widespread view that nerve-fibres grow out freely from central cells. 

 He finds that the longitudinal growth of nerves comes about by 

 mitosis in a chain of elements (the " nerve-fibre-cells "), whose nuclei 

 have been previously regarded as the nuclei of Schwann's sheath. A 

 nerve-fibre is a multinucleate neurofibrillar syncytium inclosed in a 

 medullary mantle. 



* Bull. Soc. Zool. France, xxxiii. (1908) pp. 57-9. 



t Arch. Mikr. Anat., lxxii. (1908) pp. 1-46 (2 pis., 7 figs.). 



\ Anat. Auzeig., xxxii. (1908) pp. 445-8 (5 figs.). 



§ Tom. cit., pp. 448-55 (7 figs.). 



|| SB. k. Preuss. Akad. Wiss. Berlin, 1908, pp. 166-77. 



