THE DESCENT OF THE RIO GY-PARANA 245 



was the end of the survey, Barao de Melgago being the 

 name of the last station, and a force of about fifty men 

 were engaged cutting an opening for the continuation of 

 the line. At the rate they were working it was estimated 

 that the line to Manaos would be completed in about two 

 years. 



We had expected to find a craft of some kind awaiting us 

 so that we might immediately pursue our journey down the 

 river, but in this we were disappointed, although, as it later 

 developed, a boat was then on its way to us, sent by order 

 of Colonel Rondon. There were only two small dugouts 

 available, which were entirely inadequate for our purpose, 

 so the men were put to work cutting down a tree of large 

 size and hollowing out a canoe which would hold the party 

 and the necessary luggage. This work we estimated would 

 take some weeks, so in the meantime we busied ourselves 

 exploring the country in the vicinity of Barao de Melga^o. 



A short reconnoissance through the forest revealed a 

 veritable zoological wonderland. I was consequently very 

 glad that we were delayed, as this gave me an opportunity 

 to study the fauna of a zoologically unknown region, and 

 to work on some of the problems of nature with which we 

 are constantly confronted, but of which so little is known. 

 One of the facts that no field-naturalist can fail to have 

 thrust upon his notice is the exact precision and nicety 

 with which the balance in nature is preserved. Take the 

 familiar example of the oyster. In its early stages of de- 

 velopment it is subject to the raids of such a host of ene- 

 mies and adverse conditions that out of a million eggs only 

 a few bivalves reach maturity; to offset this wholesale de- 

 struction nature has provided that a single oyster may 

 lay several millions of eggs, and thus the race is preserved. 

 Birds, to a less extent, are subject to this same thoughtful 

 provision; therefore we find that the species which are sub- 

 ject to many dangers during the nesting-period or which 

 undertake long, perilous seasonal migrations, lay compara- 

 tively large sets of eggs; this is best evidenced by ducks 



