510 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
comes to the surface voluntarily to swim about. When freshly captured 
Nautili are placed in aquaria they rise to the surface and sink to the 
bottom with the greatest facility. The rising is effected solely by the 
muscular activity of the animal, and is in no w r ay clue to tlio physical 
modification of the gases in the air-chambers. The arteries and veins in 
the mantle are described in some detail ; the latter are said to simply 
riddle the mantle in a manner which defies one’s power of draughts- 
manship. 
As Dr. Willey desired to obtain experimental evidence as to the 
physiological significance of the siphuncle of the Pearly Nautilus, he 
made several successful attempts to cut it without otherwise injuring the 
animal. His evidence cannot be regarded as conclusive, but it is clear 
that the cutting of the siphuncle does not seriously affect the vitality of 
the animal, nor does it prevent it from making movements of translation, 
or from floating at the surface, or from sinking to the bottom. The 
siphuncle would appear then to be of the nature of a vestigial structure, 
and it is legitimate to suppose that the course of evolution has led to a 
reduction of this organ pari passu with an increase in the efficiency of 
the chambers as hydrostatic organs. During the process of reproduction 
the female Nautili appear to live in retirement and to practise what the 
Germans call Brutpflege. It is almost certain that reproduction takes 
place all the year round. The blood is a syrupy fluid with a pronounced 
blue tint, which becomes very dark on exposure to the air. 
There is a further note on the nepionic shell. From the size of this 
shell, which comprises a large number of chambers, there is strong 
presumptive evidence that the animal of Nautilus, at the time of hatching, 
has the main features of the adult with the possible addition of a yolk- 
sac. Attention is also drawn to some variations in the shell of 
Nautilus, and these variations may be either single, collective, or 
incomplete. 
In conclusion, a table is given of the species and varieties of the recent 
Nautilus. 
y. Gastropoda. 
Spermatocytes of Helix.* — Mr. A.Bolles Lee continues his account 
of the history of the changes which occur in the spermatocytes of the 
snail. He has already shown that at the end of kinesis the equatorial 
portion of the spindle undergoes degeneration, and becomes converted 
into an intercellular bridge, which unites the two daughter-cells. He 
now shows that the polar portion of the spindle undergoes a similar 
degeneration, which converts it into the body described by some authors 
as the “ Nebenkern,” and by others as the “ attractive sphere.” This 
body totally degenerates and disappears in the cytoplasm, during the 
prophases of the new kinesis, in which it plays no part. Thus it follows 
that the whole of the spindle undergoes a retrogression which causes its 
elements sooner or later to be incorporated in the cytoplasm, without its 
having played any part in building up the new spindle. The spindle is 
formed entirely by and in the nucleus, in consequence of the transforma- 
tion of the karyoplasm into a special substance, which the author calls 
“ substance fusoriale.” 
* La Cellule, xi. (1896) pp. 225-60 (1 pi.). 
