COE: TERRESTRIAL NEMERTEAN OF BERMUDA. 551 
In order to account for the great diversity of conditions occurring 
in the sexual phases observed, it seems necessary to assume: the 
appearance of (1) large females, and perhaps smaller males, in the 
earlier part of the reproductive season; (2) hermaphroditic forms, 
appearing somewhat later, some of which first discharge their 
spermatozoa and subsequently develop the ova which give rise to 
embryos within the body; (3) hermaphroditic forms which mature 
eggs and embryos before the discharge of the spermatozoa, then in 
part become transformed into (4) small males with large spermaries, 
and in part form (5) separate gonads, some of which contain sperma¬ 
tozoa that mature the same season, others ova that remain undevel¬ 
oped until the following year, the individual then being again recog¬ 
nized as (1) a female form. Careful study of the worms throughout 
all seasons of the year is needed to determine with certainty the 
exact significance of all the sexual conditions observed. 
Reproduction. 
As has been stated above, the species is hermaphroditic and vivip¬ 
arous, the young worms at the time of birth being of large size 
and provided with practically all the organs of the adult except the 
sexual glands. 
But few other species of nemerteans are as yet known to be 
viviparous, and most of these probably belong to the genus Proso- 
rhochmus Keferstein, although several of them have been placed in 
other genera, and two of them, which have not been fully studied, 
belong to the Heteronemertea. 
The distribution of the known viviparous forms is as follows :— 
Prosorhoclimus claparedi Keferstein. Mediterranean Sea, north¬ 
ern coast of France and England, and possibly the Black Sea. 
Prosorhoclimus korotoneffi Burger. Mediterranean Sea. 
Borlasia vivipara Uljanin = Monopora vivipara Salensky. 
Black Sea. Probably belongs to Prosorhoclimus. 
Borlasia maslovskyi Czerniavsky. Black Sea. 
Tetrastemma ohscurum Max Schulze. Baltic Sea. 
Tetrastemma lacustre Du Plessis = Stichostemma lacustre. Lake 
of Geneva. 
TAneus viviparus Isler. Juan Fernandez. According to the 
collector, Dr. Plate, the young are born alive. 
