258 
W. M. Wheeler 
A modification of this early view was introduced by v. Wille- 
moes- Suhm ('75) in a letter to v. Siebold from the Challenger 
Expedition. In this letter he announces the discovery of encysted 
Myzostomes. In each cyst, or gali were found «stets zwei Myzostomen^, 
ein großes Individuum, das viel dicker ist als irgend welche, die 
ich früher frei auf den Armen des Seesternes fand, und ein kleines, 
das etwa nur ein Fünftel des vorigen misst, ganz dünn und platt. 
Das ist Alles, was ich bis jetzt als sicher annehmen kann, da ich 
die dickeren Exemplare noch nicht genauer untersucht habe. Es 
liegt aber sehr nahe, an die sogenannten Männchen und Weibchen 
von Distoma Okenii in den Kiemenhöhlen von Brama Rayi zu denken 
und anzunehmen, dass auch hier das eine Thier sich namentlich für 
die männliche, das andere für die weibliche Thätigkeit entwickelt, 
jedenfalls ist es interessant zu sehen, dass Myzostomum sich ganz 
wie gewisse Trematoden [Monostomum faha^ Distomum ferox etc.) 
paarweise encystiren kann, ein Fall, der bei den Myzostomen an 
den europäischen Küsten bisher meist beobachtet worden zu sein 
scheint(f. This interesting Observation was, so far as the sexual re- 
lation of the two encysted Myzostomes was concerned, only a shrewd 
guess, since v. Willemoes -Suhm, according to his own statement, 
had not been able to study the internal anatomy of his specimens. 
A few years later v. Graff (77) in his monograph of the genus 
accepted the view of the older authors and gave a very good account 
of the reproductive organs. Like some of his predecessors he observed 
small individuals of M. glahrum attached to the anterior dorsal region 
of the larger ones, and he correctly interpreted the former as the 
young of the latter. 
The unusual position of the young individuals was supposed to 
be due to a desire on their part to get as near as possible to the 
food current passing into the mouth of the Crinoid. They were 
supposed to attach themselves to the disc of the Crinoid on reaching 
a certain size. v. Graff did not study the sex of the young 
individuals. 
In another paper ('83) v. Graff gave the first account of the 
sexual phases in cysticolous forms [M. cysticolum^ inßatorand Murrayi), 
and in a somewhat later contribution ('84 b), describing the fine series 
of specimens obtained by the Challenger Expedition, he gives a 
1 This species was afterwards described by v. Graff as M. tenuispinum 
('84b, pagg. 68—70). 
