176 



censes, the tirle overwhelms the current of the river, and forces 

 its way up the course ; little by little a barrier ' f sand is thrown 

 up, which, af'er a shoit time, completely shu^s out the sea. 

 This wntcr that is now shut offsets a small supply from occa- 

 sional shnwcrs of rain or from the sea at sprintr ti(^e, so that 

 about i'ebruaiy and March the comp >sition of the water of the 

 lagoon is as foil 'ws : The lower part consists of a basin of 

 brackish water of about 'it to 40 yards in breadth and I mile or 

 less in hmgth. with the corresponding flora and fauna ; even 

 miniature mangroves grow here. T wards the hills the bed of 

 the ravine becomes narrower and the water sweeter ; and not 

 very much higher up the water is entirely sweet, a fact clearly 

 proved by the fauna and flora. In this water, for which I have 

 no other criterion than the flora and the taste, a curious fauna 

 reigns Numerous tadpoles cover the bottom and the water 

 plants in black lumps ; quantities of dipterous larvae of different 

 genera are swimming about, dragon flies larvge and water beetles 

 dart hither and thither, and among these, just as numerous, 

 if not in larger numbers, Mi/sis, Nereie and small Medusas, 

 together with Palaemonidae and a small kind of Atya, not to 

 forget the rhabdocaelous Turbellaria are to be noted. The 

 Mysidae are generally found in brackish water, but here they 

 seem to thrive well in the sweet water, Avhich is proved not only 

 by their large numbers, but also by the fact that many were 

 carrying their eggs about, with them. But what is most strik- 

 ing, and is also applicable to the other animals mentioned, is 

 that they are not to be found or at least sparingly in the salt 

 part of the lagoon. The Nereidae, a small form of about 15 m.m., 

 was also found in large quantities. Among the plants, the little' 

 Medusae, of about 2 m m. diameter, were swimming nbaut. 1 

 do not think that this Medusa is identical Avith the sweet water 

 Medusa described by i^ay Lankester ; I only found young speci- 

 mens, so that I could not c 'mpare them with those described by 

 Ray Lankester ; but it is of importance that they were found for 

 the rirst time in nature in sweet water, which circumstance gives 

 an idea of the origin of those found in England Im a hot house. 

 Strange to say I could not find the hydroid stocks belonging to 

 these }iledu«ae, although a very careful search was made. It is 

 curious to note that the inhal.itants of the sea were only fouud 

 in that part of the lagoon whc^re there was no current. 



Above I spoke of the small size of the inferior SAveet water 

 fauna in comparison with the European one; but it is just the 

 contrary with the Land fauna ; the giants of the inferior land 

 fauna are found in- the Tropics, such as snails, earthworms, 

 Myrinpodes, Arachnidae and insects ; but what is most curious 

 about these is that some of tho nearest relations are found only 



