267 
1916-17.] Experiments and Observations on Crustacea. 
the last two epimera separated and the preceding jive fused, acquires a 
new interest. 
Merely to state a problem is not to solve it ; but already by implication 
a shrewd blow has been dealt at the presumed degree of consanguinity 
underlying one of the systematists’ generic criteria ; a number of further 
problems has also been suggested. 
Glyptonotus evidently moults after the fashion of other isopods. 
Among the specimens in the Oceanographical Laboratory two were found 
to have just completed full moult, the half of the body anterior to the usual 
transverse line of split being still quite soft. A considerable number had 
obviously undergone complete moult at no long date before capture, the 
body being rigid but fragile. No specimens were at the stage just 
subsequent to posterior and prior to anterior moult. 
The last-mentioned fact is not surprising when one considers that the 
locomotor apparatus is almost limited to the posterior half of the body. 
In the state of half-moult a Glyptonotus would presumably be in an 
unusually helpless condition, having for a time at least only the fourth 
pair of perceopods by which to row itself along. Seeing that there exists 
a special relation between moulting and locomotion in isopods, and seeing 
that three pairs of walking limbs in Glyptonotus have been transformed 
into prehensile organs, observations on the behaviour of the animal during 
moult would be of exceptional interest. It may be that the moult sets a 
limit to the number of isopodan limbs that can thus be modified, and also 
that it determines the general balance between the half of the body behind 
and that in front of the fifth thoracic segment. 
As was probably inevitable, no evidence bearing on the meaning of the 
present “ generic ” separation between Glyptonotus and Chiridotea was 
obtained from the dead specimens. Whether these two branches of Miers’ 
u Subfamily ” owe their present external similarity to direct heredity or 
to convergence is a point that cannot be settled offhand, even though 
Chiridotea should be found off Florida and also in the Caspian Sea. Some 
biologists might perhaps be willing to assume, and even to defend, a purely 
hereditary connection in such a case ; this makes it all the more necessary 
to keep an open mind and to refuse to admit unproved assumptions. In 
this connection, cf. also Racovitza and Sevastos (1910). 
Inter somitic Articulations. — In flexion and extension of the thoracic 
segments upon each other the movement at each articulation occurs about 
a transverse axis, which in each case is situated more ventrally than 
dorsally. In correspondence with this arrangement, the intersegmental 
cuticle on the dorsal aspect is long and loose, being folded inwards between 
