The Sexual Phases of Myzostoma. 
229 
this may be left to future investigators; for the purposes which 1 
bave in view I propose to group the species according to tbeir ha- 
bits, thus: 
I. Migra tory species; i. e. species which move aboui freely on 
the Crinoids which they infest. Type: M. cirriferum^ Leuck. 
IL Stati onary species; i. e, sluggish species which rarely if 
ever leave the spot where they bave settled on the Crinoid. Type: 
M. glahrum^ Leuck. 
HI. Cyst-producing species; i.e. species which produce galls 
or swellings on the discs or arms of their Crinoid hosts. Type: M. 
cysticolwn^ v. Graff. 
IV. Entoparasitic species; i. e. species which inhabit the 
alimentary tract of their Crinoid hosts. Type : M. pulmnar^ v. Graff. 
Ali the species of these various groups may be arranged in a 
series of increasing parasitism, or, strictly speaking, commensalism, 
from the primitive and most typical forms of the first group to the 
very aberrant species of the fourth group. The departure in the 
adult from the juvenile condition increases in a corresponding manner: 
the young and adult of forms like M. cirriferum being very similar, 
w^hile the young and adult of M. imlmnar are very dissimilar. The 
nine species which I shall consider in the present paper may be 
distributed among the four groups as follows : 
M. cirriferum^ Leuck. 
M, circinatum^ n. sp, 
^ . . \ M. qlahrum. Leuck. 
II. Stationary species j ^ ^ ^^^^ 
M- platypus, v. Graff. 
M. belli, n. sp. 
M. cryptopoditwi, n. sp. 
M. eremita, n. sp. 
IV. Entoparasitic species { M. pulvinar, v. Graff. 
1. Migratory species 
III. Cysticolous species 
1. Myzostoma cirriferum, Leuckart. 
The habits and general structure of this commonest of the 
Mediterranean species of Myzostoma bave been so fully described 
by LovÉN ('42), v. Graff (77), Nansen ('85) and others, that I 
may bere restrict my account to the reproductive organs and the 
sexual phases. Düring February and March nearly ali the specimens 
16* 
