38 
AUSTRALASIAN ANTARCTIC EXPEDITION. 
Patagonia was separated from Chili by a strait of considerable breadth. The 
present Magellan fauna was considered to consist in part of forms derived from 
the Tertiary fauna of that district and in part of recent immigrants from the north 
along the Pacific coast of America, and from the south (Kerguelen district) along the 
coast of the Antarctic Continent. Von Ihering recognised that the climate of the 
early Tertiary in Patagonia was warmer than that of the present day. 
Blochmann (1908) discussed the possibilities of migration possessed by Brachio- 
pods and their larvae, and arrived at most interesting conclusions, which appear well 
founded. In the adult stage the animals are fixed to some object by their peduncle 
and locomotion is precluded. They are frequently swallowed by fish, and may be 
subsequently disgorged alive, but the chances of their living in the stomach of a fish 
while being carried any great distance, and the further chance of both male and female 
individual being thus planted close to one another, are so small as to render such a 
method of transference quite negligible. There remains only the distribution effected 
during the free swimming larval stage. In this respect a distinction must be drawn 
between Lingula and Discina (sensu lato) on the one hand and the rest of the class 
on the other. 
Lingula and Discina. have pelagic larvae furnished with a mouth and a functioning 
stomach. Nevertheless only one species, the deep-sea form Pelagodiscus attanticus, is 
cosmopolitan in its distribution. The narrower distribution of other species is probably 
conditioned by the fact that they are adapted to shallow bottoms in warm waters. 
Discinisca lamellosa is frequently found in great groups, which seems to show that the 
larvae have not swum far, and the young of Discinisca Icevis frequently also rest on 
adult shells. 
So far as is known, the larvae of other Brachiopods are not pelagic, and have 
not been found in the plankton of higher levels of the sea. Blochmann has himself 
repeatedly searched for them at the season of reproduction without success around 
the Norwegian coasts where Brachiopods are common, and he concludes that they 
remain near the bottom and settle down not far from their mother. This must 
especially be the case for the deeper forms which are below the effective action of 
currents. 
The organisation of the larvae of the species in question precludes a long duration 
of the free-swimming stage. With the exception of Lingula and Discina* they are 
all, as far as known, without a mouth and functioning stomach during this stage, and 
must consequently soon come to rest. Actual observations on two species of 
Terebratulina show that the larvae settle after ten to twelve days. 
From these facts Blochmann concludes that the power of distribution of 
Brachiopods is very limited, and that the larvae are unable to cross the oceans from 
one coast to another. Only a few species live in depths of over 2,000 metres (roughly 
* Little is known of the larvse of Crania. 
