The Sexual Phases of Myzostoma. 
285 
rudimental or obliterated concomitantly in some cysticolous and 
entoparasitic Myzostomes (e. g. M, puhinar). 
Beard ('84) bas given a very different interpretation of tbe 
male ducts from tbe above. After attempting a reduction of tbe 
oviduct (i. e. tbe median dorsal opening of tbe body-cavity) to a 
pair of nepbridia, be goes on to say (pag. 566) tbat tbe »two male 
ducts are mucb more easily referable botb from position and struc- 
ture to segmental Organs wbicb still open into tbe body-cavity«. 
Wbile tbe reduction of tbe oviduct to a pair of nepbridia bardly 
requires serious consideration, tbe bomology of tbe male ducts witb 
nepbridia is not so easily refuted. As Beard bimself, bowever, now 
interprets Nansen’s lateral oviducts as nepbridia ('94), be would 
probably abandon tbese earlier bomologies, unless, indeed, be sbould 
assume tbat two pairs of nepbridia bave been retained in tbe My- 
zostomidae. 
5. Parapodia and Cirri. Tbe resemblance of tbe cirri and 
parapodia of Myzostoma to tbe bomonymous structures of tbe Cbae- 
topoda bas often been pointed out, and I sbould not bere allude to 
tbe subject, were it not to call attention to two structures wbicb 
bave not been sufficiently considered by preceding autbors and 
wbicb make tbe resemblance still more striking. Tbe first structure 
is tbe ventral cirrus of tbe parapodium. Tbis I believe to be 
present in at least two, and possibly in tbree, species of Myzostoma. 
In M. circinatum tbe small, pointed and somewbat curled cirri in- 
serted on tbe inner bases of tbe parapodia (PI. 10 Fig. 18) are 
in all probability typical ventral cirri, readily bomologized wdtb tbe 
ventral cirri of Polycbaeta. In M. platypus (PI. 11 Fig. 27) tbe 
beart-sbaped elevations witb broad bases of attacbraent are probably 
only anotber form of ventral cirri, wbicb, curiously enougb, seem to 
bave undergone a modification comparable to tbat of tbe dorsal cirri 
(elytra) in Cbaetopods like Lepidonotus and Tomopteris. I also deem 
it probable tbat tbe peculiar pedunculate cups at tbe bases of tbe 
parapodia in M. calocotyle^ v. Graff may represent a tbird form of 
ventral cirri. v. Graff ('84b, PI. 3 Figs. 25 and 26) regarded tbem as 
»suckers«, but I find it very remarkable tbat segmental sacs sbould 
occur, not between and some distance dorsal to tbe parapodia, but 
attacbed to tbe bases of tbe parapodia. Moreover v. Graff figures 
five of tbese cup-like Organs on one side of tbe body! 
Tbat tbe twenty cirri wbicb fringe tbe edge of tbe disc-like body 
in most Myzostomes are to be regarded as bomologues of tbe 
