2 
\V. E. AGAE. 
primarily for this purpose. The spot where the Lepidosirens 
were collected was a station of the South American Missiouary 
Society called Naktetingma, about ninety miles west of 
Villa Concepcion, and about a league from the spot which 
Prof. Graham Kerr made his headquarters while collecting 
his material for working out the embryology of this fish. It 
is to him that I owe the whole idea of making this expedition. 
The expenses of the expedition were defrayed by the 
Government Grant Committee of the Royal Society and by 
the managers of the Balfour Fund of the University of 
of Cambridge, to both of which bodies I should like to take 
this opportunity of conveying my thanks. I should also like 
to acknowledge my indebtedness to the South American 
Missionary Society for the help they so cordially gave me, 
and especially to the little band of missionaries at Nakte- 
tiugma, who most generously provided me with horses, 
waggons, bullocks and a home during the whole of my stay 
in the Chaco, and more important still, procured Indian 
hunters for me, and, in fact, ensured the success of the 
expedition. 
I arrived in the Chaco in September, 1907, at the end of 
an unusually prolonged dry season. As is well known, 
Lepidosiren burrows into the mud at the bottom of the swamps 
when these dry up, and remains there in a torpid condition 
till the next rainy season sets in — normally a period of about 
six months. The years 1906 and 1907 were, however, 
unusually dry ones in the Chaco, and I was informed by the 
missionaries that for more than a year before my arrival 
there had not been enough water in the swamps to bring out 
the Lepidosirens — or, at any rate, to keep them out long 
enough to allow them to breed. Rain began to fall soon after 
I arrived, and by the middle of October the Lepidosirens were 
swimming about in the swamps. Directly they leave their 
burrows for the water the males start growing their peculiar 
vascular filaments on the pelvic fin, a sign that they are 
about to breed, and about the beginning of November their 
nests, containing eggs, began to appear in the swamps. I 
