90 Papers from the Department of Marine Biology. 
third much smaller; flagellum composed of about 8 joints. Second antenna 
more slender than the first but not very much longer; in the peduncle the first 
two joints are very small and equal; the third is as long as the first two 
together, the fourth longer still, and the fifth about as long as the third; the 
flagellum is composed of 7 joints and extends very little beyond the lateral 
margin of the first segment. The frontal lamina is pentagonal, scarcely twice 
as long as broad. 
Maxilliped second joint much longer than those succeeding, which are very 
broad. First thoracic segment nearly twice as long as the second; the pos- 
terior six segments vary slightly among themselves. Appendages robust, all 
joints broad, with few setz. 
First segment of abdomen quite hidden below last thoracic. Telson forms 
an equilateral triangle, ending in a sharp apex with 16 to 18 spines on the pos- 
terior margin, surface smooth. Inner ramus of uropod extends a little further 
than the telson, is narrow and ends in a sharp apex; both margins are fur- 
nished with spines; outer ramus about the same length, but still narrower; 
peduncle not produced far posteriorly on inside. 
Appendix masculina slender, much longer than inner ramus of second uro- 
pod, apex rounded. 
This species is very distinct. It is separated from all others by the 
insignificant length of the second antenna, and also, so far as I can find 
from the published descriptions, by the character of the colour mark- 
ings. The shape of the telson and especially of the uropods is also very 
distinctive. 
All the members of the Cirolanine to which this species belongs 
are predatory and swim about very actively. Cuirolana lineata is far 
from being as sedentary as Synalpheus, which, while very energetic at 
times, rests for long periods on the disc of the crinoid. While the isopod 
may make busy excursions onto the surface of Comanthus, it is often to 
be seen diving into the gut of the host, where it apparently spends a 
large part of its time. It does not feed, so far as I know, on the tissues 
of the crinoid itself, but only on the food it finds in the stomach. 
It must be this or a very closely related form which Haswell refers to 
as collected from a crinoid in Torres Straits associated with Synalpheus 
comatularum and Galathea deflexipous, but no identification of his isopod 
seems to have been made. 
This case of commensalism is interesting because of the faint but 
significant response to the colour stimuli of the crinoid. In nearly all 
the species of this genus, where the colouration is noted at all, the chro- 
matophores appear to be distributed over the surface so as to form a 
series of evenly spaced dots or dashes of pigment. The concentration 
of these into lines and the development of a purplish pigment seem 
to be the first effects of the commensalism. The insignificant quanti- 
tative development of the pigment is probably associated with the very 
active life of the isopod and its frequent immersion in the gut of the 
host, rather than to any incapacity of the isopod to assume the colours 
of the environment. 
