On fresh- water Nereids from the Botanical Garden 
at Buitenzorg, belonging to Lycastis 
hawaiiensis Johnson, 
by 
D r . R. Horst x ). 
The Polychaete worms, described in the present paper, were 
forwarded to me for identification by the Department of Agriculture 
at Buitenzorg, where thejr were found in a fresh water pond of 
the Botanical garden. They proved to belong to the genus Lycastis, 
that consists of a group of Nereids, characterized by the facility, 
with which they accomodate themselves to water of a greatly 
reduced salinity. For of the eight species, belonging to this genus, 
five are living in brackish or fresh water, whereas one of them 
has a strictly fresh-water habitat. Lycastis is distinguished from 
the allied genera by : the total absence of paragnaths or soft papil- 
lae upon the proboscis and the uniramous feet (the dorsal lobe being 
entirely absent or extremely rudimentary). 
The specimens from Buitenzorg quite agree with Lycastis 
hawaiiensis, collected in a spring near Honolulu (Hawaiian Islands) 
and first described by H. P. Johnson in his interesting paper on 
„Fresh-water Nereids from the Pacific Coast and Hawaii” 1 2 ). They 
are all incomplete, lacking some of the caudal segments; therefore 
nothing could be stated about the anal cirri. The two largest 
individuals measure about 80 mm. in length, but with the want- 
ing segments they certainly reached a length of 100 mm., their 
1) . Some time ago Mr. Palmer van den Broek made us a present of two living 
Pro-echidna Bruynii (Peters et Doria) from New-Guinea. 
In order to keep these animals alive, they are chiefly fed on worms every day. 
Being requested by the Académie Impériale des Sciences de St. Pétersbourg to 
collect some species of Oligochaeta, which are found here, I continually examined 
the worms, gathered for the Pro-echidna’s, and was one day (20 September 1908) not 
a little surprised to find among them some living polychaeta. 
On a closer examination it turned out, that these polychaeta, which belong to 
the family of the Nereidae, are found in the neighbourhood of the Rhizophora, 
growing in our Botanical Garden and especially near Rhizophora mucronata Lamk. r 
Rhizophora conjugata L., and Bruguiera eriopetala W. et A. 
Most probably the worms are brought over with the mangrove plants. If so, 
then it is no doubt a very remarkable fact, that where in the last two years no 
mangrove plants have been brought from the sea shore to our gardens, these worms 
were able, not only to maintain themselves in fresh water, but even to multiply in 
these to them quite new surroundings. 
On the first of October of last year some specimens of the said worms were sent 
to the Director of „’sRyks Museum voor natuurlijke Historie” at Leyden, who gav& 
them to D r . R. Horst, to determine and describe. P. A. Ouwens. 
2) Mark Anniversary Volume, 1903, p. 205, pis. XVI and XVII. 
