94 Papers from the Department of Marine Biology. 
Von Graff quotes, however, a passage from a letter written by von 
Willemoes Suhm,* showing that myzostomids may correspond perfectly 
with their host in colour pattern. The case mentioned is that of 
Myzostoma horologium v. Graff on crinoids which were probably Coma- 
tula rotalaria and Comatula solaris. The passage runs as follows: 
“In der Arafura-See habe ich im vorigen Jahre einmal 80 Exemplare einer 
grossen Comatula untersucht und fand circa auf jeder zehnten unsere 
Schmarotzer. ... Alle dieser Myzostomen waren, wie die Comatula, weiss und 
schwarz gefleckt, und die ubrigen zahlreichen Schmarotzer des Thieres zeigten 
dieselbe Farbung.”’ 
The myzostomids found on the crinoids of Murray Island were very 
numerous and belonged to several different species. Dr.C. L. Boulenger, 
of Birmingham University, has been kind enough to undertake their 
identification. They are in many cases very brightly coloured and 
have pronounced colour patterns. Generally speaking, there are two 
types of pattern. In the first concentric rings of bright and dark 
pigment alternate. In the second the dorsal surface is ornamented 
with radiating ridges, and these are usually free from pigment or very 
light coloured. The ridges are thrown into relief by an edging of a 
dark pigment (e. g., purple or black) ; the general ground colour between 
the ridges as a rule approaches that of the crinoid on which the parasite 
was found. One of these forms was very common on the dark green 
or black varieties of Comanthus annulatum. The alternate black and 
non-pigmented rings are in vivid contrast, but the myzostomid is thin 
and the non-pigmented parts are so transparent as to be inconspicuous 
against the dark ground of the host. This species seems to occur only 
on the darker crinoids. In another species the same arrangement is 
found, but much lighter hues prevail, green pigment alternating with 
very light brown. The colours of the host were, unfortunately, not 
noted. 
When the host is very light coloured the alternation of darker rings 
does not occur. On a green variety of C. annulatum a specimen of 
Myzostma was found which matched it perfectly. The greater part 
of the body was bright green, but a few white spots represented a broken 
ring of a lighter colour; the edge was relieved by dashes of black pig- 
ment, while the cirri were brownish. A very magnificent example of 
the second type of colouration was secured on October 24, 1913, on a 
green form of C. annulatum. It resembled its host closely and was 
comparatively inconspicuous. The general colour was a bright green; 
the ridges appeared greenish white, darker at the edges owing to the 
addition of a granular pigment, and round each there was an intense 
black line. An allied form was found on darker crinoids; there the 
ridges were white or yellow surrounded by a darker line (in one case 
*yon Willemoes Suhm, Zeits. f. wiss. Zool. Bd. xxv1, 1876. 
