288 SUMMARY OF CURRENT RESEARCHES RELATING TO 
The likeness between the Amphibian and Reptilian type illustrates 
homoplasty or convergence. This leads the author to a short essay on 
convergence, in which he distinguishes (a) direct convergence, in relation 
to similar function, e.g. the worm-like shape of burrowers ; ( b ) indirect 
convergence, in relation to similar bionomic conditions, e.g. the white- 
ness of many arctic animals ; and (c) mimicry. 
b. Histolog-y. 
Growth of Injured Nerves.* — Prof. L. Ranvier has studied the modi- 
fications produced in the nerves of the cornea by superficial cuts, and 
corroborates a conclusion which he formulated in 1880, that nerves 
exhibit jjersistent growth. The nervous fibres of the cornea, divided by 
section, but still in continuity with their originative cells, vegetate with 
a rapidity and activity which was unsuspected. 
Effect of Poisons on Cortical Nerve-Cells, f — Dr. H. J. Berkeley has 
made an important research on the lesions produced by the action of 
certain poisons (alcohol, serum, ricin, &c.) on the cortical nerve-cells. 
What he has to say in regard to the pathological alterations in the 
nuclei and nucleoli is of some general histological interest, and so is his 
discussion of the intra-cerebral nerve-endings. 
Peculiar Ganglion-Cells in Spinal Cord of Perch.t — Dr. R. Kolster 
has studied the minute structure of the spinal cord in numerous Teleostei, 
and has found peculiar nerve cells in Perea fluviatilis, which he suspects 
may be associated with the raising and sinking of the dorsal fin. They 
seem to be absent from other Anacanthini, but there are somewhat 
similar elements in the angler. 
Optic Nerves of Fishes-§ — Dr. K. Krause has studied these nerves 
experimentally in the gold-fish ( Cyprinus auratus), and finds that there 
are several kinds of fibres. The main mass arises from retinal cells, 
and atrophies when the eye is removed. These fibrse ocular es perhaps 
end in small part in the ganglion geniculatum laterale, but for the most 
part they end in the external and internal tract in the median grey 
matter of the tectum opticum. From cells in this region, especially from 
the most dorsal portion between the two tracts of optic fibres, there arise 
some fibrse tectales , which may be followed into the chiasma and form a 
small part of the optic nerve. 
Electric Organ of Torpedo. || — Dr. Fr. Cre vatin discusses the so- 
called Stabchennetz in the electric organ of Torpedo marmorata, — an 
organ which has been the fruitful source of histological controversy for 
forty years, since Remak’s description in 1856. The author worked with 
the quick Golgi method, and has been forced to deny the existence of 
the Stabchennetz ; it is nothing but the nervous terminal network, faintly 
coloured. 
Osmotic Phenomena in Mitosis.^T — Prof. F. Houssay argues in favour 
of the hypothesis that the attractive sphere is the centre of osmosis, as 
* Comptcs Benclus, exxv. (1897) pp. 1001-8. 
f Johns Hopkins Hospital Reports, vi. (1897) pp. 1-108 (15 pis.). 
X Anat. Anzeig , xiv. (1898) pp. 250-3 (1 fig.). 
§ Arch. Mikr. Anat., li. (1898) pp. 820-39 (1 pi.). 
|| Anat. Anzeig., xiv. (1898) pp. 213-50 (2 figs.), 
ii Tom. cit., pp. 305-10 (7 figs.). 
