TRANSACTIONS OF SECTION D, 783 
when covered by water. Those which are placed high up in the tidal zone are 
not so well nourished as those which have a lower position. ‘The former have less 
time during which feeding is possible, and are much smaller in size than the latter. 
Mussels have the sexes separate. Their larval free-swimming stage ceases before 
sex is differentiated, as far as can be made out by histological examination. There 
is not a relatively greater number of females in the middle and lower zones, nor a 
relatively greater number of males in the higher zones. The inference is that in 
the mussel nutrition has no influence in determining sex. 
The common limpet (Patella vulgata) is also found everywhere in the tidal 
zone. Its sexes are separate, and the free-swimming stage ceases before sex is 
differentiated. The limpet is not fixed in the same sense as the mussel, but from 
its habits it may be considered as practically fixed. 
The same facts regarding the numerical proportion of males and females at 
different levels were found to hold good for the limpet as for the mussel, and the 
same inferences were drawn. In the mussel and the limpet there are no well- 
marked secondary sexual characters, and the ovary and testes are equal in bulk, 
On the other hand, in the special animals in which nutrition has been distinctly 
shown to influence the determination of sex there isa disproportion sometimes 
extreme between the amounts of the male and female sexual products. This is 
due chiefly to the fact that the eggs in these cases are provided with much deuto- 
plasm, while the sperm is small in amount. The presence of deutoplasm in large 
quantity cannot, however, be considered to be primitively characteristic of ova. 
Bearing of the foregoing on the general questions of the evolution and deter- 
mination of sex. 
3. Lxhabition of Newly Discovered Remains of Neomylodon from Patagonia. 
By F. P. Moreno and A. Suira Woopwarp, 
On behalf of Dr. F. P. Moreno, Director of the La Plata Museum, Mr. A. Smith 
Woodward exhibited some newly discovered remains of the supposed extinct 
ground-sloth Neomylodon, discovered by Dr. R. Hauthal in a cavern in Patagonia. 
The animal had previously been known only by a piece of armoured skin from the 
same cavern. The new specimens ccmprised a skull, evidently broken by man, 
and some well-preserved pieces of exciement. These were found beneath a layer 
of earth in the cave, with a large quantity of hay and other evidence of the pre- 
sence of man. The excrement showed that the animal fed on grasses and herbs, 
not on the foliage of trees. The skull, which still showed pieces of flesh and carti- 
lage adhering to it, seemed to be identical with one from the Pampa formation 
further north, named Glossotherium or Grypotherium, as already observed by Dr. 
Santiago Roth. The theory of Dr. Hauthal, that these ground-sloths were kept 
in captivity in the cave by the ancient Patagonians, was adversely criticised by 
several speakers, and the fresh appearance of the specimens was specially com- 
mented upon. 
4, Exhibition of and Remarks on a Skull of the extinct Chelonian Miolania 
Srom Patagonia, By F.P. Moreno and A. Smrra Woopwarp. 
Mr. Smith Woodward also exhibited, on behalf of Dr. Moreno, a skull of the 
extinct Chelonian reptile, Miolania, obtained by Dr. Roth for the La Plata 
Museum during his recent expedition to Chubut. The skull proved to be 
essentially identical with others already discovered in superficial deposits in 
Queensland and in Lord Howe's Island, 400 miles off the coast of New South 
Wales. The discovery was thus of great interest, as apparently favouring the 
hypothesis of a former great antarctic continent, of which Australia and Patagonia 
are now mere remnants, 
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