132 
COLOUR IN NATURE 
CHAP. 
bergi has similar blue spots arranged in radiating 
lines. In Diddema the spots have been called eye- 
spots. 
4. Crinoids. —The Crinoids are remarkable in 
showing great individual variation in colour. During 
life the colours are usually brown, red, purple, violet, 
green, yellow or white, but the curious form called 
Holopus is of a jet-black colour. Agassiz remarks 
that the colours of the deep-sea and shallow-water 
forms show remarkable similarity. 
As to individual variation in colour Moseley notes 
that during the voyage of the Challenger he found 
specimens of Pentacrinus which were purple, and 
others which were yellow or pale-coloured. Agassiz 
noticed the same thing in both Pentacrinus and 
Rhizocrinus , while Malard describes it in greater 
detail for Comatula. Malard found a large number 
of specimens of the rosy feather-star on a buoy near 
La Hougue which were of three distinct colours, 
violet-red, orange-red, and white and red with reddish 
pinnules. Clinging to the feather-stars, Malard found 
numerous specimens of the Crustacean Hippolyte , 
and he states that “at least in the majority of 
instances” the prawns resembled their neighbours 
so much in tint that it was exceedingly difficult to 
distinguish them. Malard regards this as an ordinary 
case of colour resemblance, but it is also interesting 
on account of the numerous analogies which exist 
between the colours of the Echinoderms and the 
Crustaceans. We find in the two groups not only 
similar colours, but also a similar range of variation. 
As we shall see, the variation in Crinoids is not 
merely apparent, but is a question of pigment. 
