24 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
( Eiscliwiele ) found in all birds, in crocodiles and tortoises, and in Trachy- 
dosaurus, for this is merely a horny epithelial organ. 
Life-history and Development of Food and other Fishes.* * * § — Prof. 
W. C. MTntosli gives us another series of his interesting contributions to 
this important subject. He begins with a number of details as to 
young Pleuronectids, and after describing an unknown post-larval form, 
proceeds to describe the eggs of the Halibut, which have hitherto 
escaped detection, when ripe ; they were obtained by Mr. Holt at 
Grimsby. A few unfertilized eggs of the Green Cod have been observed. 
The eggs of the Pollock and Torsk are next discussed, and they are 
followed by some notes on the development of Arnoglossus megastoma. 
Among the remaining subjects on which Prof. MTntosh has notes are 
the development of the Brill and the eggs of Lophius. 
Ovary and Intra-Ovarian Egg of Teleosteans.j — Mr. W. L. Calder- 
wood, who has examined the ovaries of eleven species of Teleosteans, has 
most complete series of sections of the ovaries of the common dab 
( Pleuronecies limanda) and the hake ( Merluccius vulgaris). It would 
appear that, in all ripening ovaries, ova for three consecutive spawning 
periods are present, and the ova may, therefore, be spoken of as great, 
small, and minute. These are described in order. 
Eggs and Early Stages of Rhombus maximus.J — Mr. E. W. L. 
Holt has been able to make some observations on the early stages of 
the Turbot. The usual diameter of the egg is 1*01 mm., and the oil- 
globule is nearly always *21 mm. The yolk is colourless and homo- 
geneous ; the markings of the zone form an open network of no regular 
pattern. The few larvrn which were successfully hatched out lived but 
a few days ; there is a general tendency in the Turbot’s egg to sink 
sooner or later after fertilization, and it is prophesied that the suc- 
cessful culture of a pelagic ovum which assumes a demersal nature at 
an uncertain period will be difficult. 
The most peculiar feature of young turbot is the cephalic armature, 
and Mr. Holt points out the interest of a Pleuronectid passing through 
a stage in which its cephalic armature is as powerful as, and for the most 
part homologous with, that of a Percoid or Scorpsenoid. 
0. Histology. 
Invisibility of Living Nuclear Structures. § — Prof. W. Flemming 
discusses several cases in which living cells and nuclei show almost no 
structure, though that becomes evident enough after death or after simple 
technique. Such are the spermatocytes of Amphibia, the nuclei of the 
so-called poison-glands of the skin of Urodela, the nuclei of the salivary 
cells of Chironomus plumosus, the germinal vesicles of the ovarian ova 
of Ascidians, and others. But as the invisible structure is readily made 
manifest when the elements are killed and treated with simple reagents, 
the constancy of the observed phenomena is surely an argument against 
regarding post-mortem appearances as artificial. 
* Tenth Ann. Rep. of the Fishery Board for Scotland, 1892, pp. 273-322 (4 pis.). 
t Journ. Marine Biol. Assoc., ii. (1892) pp. 298-312 (2 pis.). 
X Tom. cit., pp. 399-404. 
§ Amit. Anzeig., vii. (1892) pp. 758 -G4. 
