574 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Placenta of Dugong.* * * § — Prof. Sir W. Turner has been able to show 
that the placenta of Hcilicore Dugong is not, as Halting suj)posed, 
diffused, but is truly zonary ; at the same time it is certain that it is in 
whole or in great part n on-deciduate, so that we now know of two types 
of zonary placenta, the deciduate, found in Carnivora, Pinnipedia, 
Elephas, and Hyrax, and non-deciduate in the Dugong, and probably 
also in the Manatee. 
Development and Life-histories of Teleostean Pood- and other 
Fishes. t — Prof. W. C. MTntosh and Mr. E. E. Prince have published 
the results of several years 5 labours at St. Andrews Laboratory. They 
endeavoured to examine as thoroughly as possible the ovarian growth, 
oviposition, hatching, and development of such of the important white 
fishes as could be obtained, and to fill up the gaps in our knowledge of 
the period between the escape of the embryo from the egg and the young, 
though advanced, forms known to naturalists and fishermen. The ova 
of about forty British fishes have been examined ; some of them were 
pelagic or floating as of the Turbot, Plaice, Flounder, Sole, Whiting, 
and Sprat, and others non-pelagic or demersal as of the Herring, Smelt, 
Salmon, Stickleback, and Sea-Bream. 
The mature ovum is first treated of, and there are remarks on the 
reproductive organs and period of spawning ; extrusion and deposition, 
segmentation, the blastoderm, the periblast, the embryonic shield, the 
general development of the trunk, the fins, the embryonic, larval, and 
post-larval stages, general remarks, and a history of Anarrliichas lupus 
form the subjects of successive chapters. The reader must be referred 
to the memoir itself for the numerous details which it contains. 
£. Histolog-y.j 
Nuclear Modifications which affect the Nucleolus.§ — M. E. 
Bataillon describes some early stages in the histolysis of Amphibians, 
which may be well studied in the cutaneous elements of the tail, though 
they are to be seen in other tissues also. Elongated elements may be 
found, of which the upper extremity is swollen like a club and contains 
the nucleus ; starting from it is a thread which becomes intensely 
stained by nuclear reagents, passes into the handle of the club, and 
extends more or less towards the base. The following stages of the 
phenomenon may be observed : — The nucleolus becomes pushed to the 
periphery of the nucleus, and appears to protrude a process about 
double its own diameter ; above the nucleus is a kind of rod which half 
surrounds it, and still arises from an internal nucleolus; the most 
varied free forms surround the nucleus and end in a swelling. The 
author thinks that the normal chromatic filament may be developed at 
the expense of the plasma of the nucleolus by absorbing grains of 
chromatin, while the nucleolar filament may be formed by a condensa- 
tion of the hyalo-plasmic framework, of which the nucleolus is in some 
* Trans. Roy. Soc. Edinb., xxxv. (1890) pp. 641-62 (3 pis.). 
t T. c., pp. 665-946 (28 pis.). 
+ This section is limited, to papers relating to Cells and Fibres. 
§ Comptes Rendus, cx. (1890) pp. 1217-9. 
