288 
REPORT ON ZOOLOGY, MDCCCXLII : 
ganglions, united by a cross band ; four threads go to the anterior parts 
from these ganglions, two of which can be traced into the large eyes. 
Dujardin also has found a similar organization in another species of 
Nemertes. 
Leuckart has given a copious account of the remarkable genus, 
Myzostomum, which lives as a parasite upon the Comatula, aud forms 
a link between the Annelides and Trematoda (Zool. Bruchst. iii. 1842 ; 
Helminthologische Beitr. p. 5). 
He characterizes this genus, founded by himself, as follows : — Corpore 
molli, clypeiformi ; supra depresso vel convexo, infra organis suctoriis et 
motoriis, tarn acetabulis (s. bothriis) quam hamulis corneis 10, in- 
structo ; ore antico, simplice, prominente (tubuloso ?) retractili. As 
Leuckart only examined specimens preserved in spirits of wine, many 
parts of the structure have remained concealed from him, so that his 
views of these parasites may be incorrect. The examination which 
Loven has made of living individuals (Arch. 1842, B. i. p. 306, and Ann. 
d. Sc. Nat. t. xviii. p. 291, and Amtlich. Ber. iiber die 19te Versamml, 
deutscher Naturforch. Braunschw. 1842, p. 82) gives us a very good idea 
of the structure of Myzostomum, and puts us in a condition to conjec- 
ture the real use of the shrivelled-up parts seen by Leuckart. Myzos- 
tomum cirriferum, Leuck., is furnished with the following diagnosis : — 
Corpore orbiculari, margine cirrato ; acetabulis in utroque latere 5, ha- 
mulum simplicem emittentibus ; hab. in mari septentrionali, Comatulae 
europseas parasitus. Loven has frequently found this species on Coma- 
tula europoea on the west coast of Denmark. The whole surface of 
the body, the margin of which is covered by twenty cirri, shows vibra- 
tile motions. On the middle of the dorsum are two slight elevations. 
On the abdominal surface is found, anteriorly, the fleshy proboscis, 
which can be completely drawn in ; on the sides there are five pairs of 
stumps of tarsi, and between these, four pairs of acetabula ; on the 
margin of the orbicular body, on each side, are the two male sexual 
openings, and the simple vulva, together with the anus. Of the internal 
organs, Loven has described the nervous system, the intestinal canal 
with its appendages, the male and female organs of generation. Of the 
latter, the ovarium, with its ramifications, occupies the whole disc, and 
contains spherical eggs. Loven concludes, from the lively motions with 
which the spermatozoa of this hermaphrodite animal swim about in the 
water, that its eggs become impregnated by the spermatozoa after they 
are laid; with which supposition the reporter is inclined to agree, as 
the spermatozoa of these hermaphrodite water-animals stiffen in the 
v/ater. The reporter cannot help remarking, that it would have been 
most desirable, had Loven described somewhat more exactly, the ovary, 
and the difierent steps of development of the eggs of this animal, for the 
organ described by him as an ovarium, evidently resembles that organ of 
332 
