246 
Proceedings of the Royal Society of Edinburgh. [Sess. 
XV. — Experiments and Observations on Crustacea : Part IV. 
Some Structural Features Pertaining to Glyptonotus.* By 
John Tait, M.D., D.Sc. (From the Scottish Oceanographical 
Laboratory and from the Physiological Laboratory of Edinburgh 
University.) (With twenty-two figures in the text.) 
(MS. received March 8, 1917. Read May 7, 1917.) 
% 
In the immediately preceding paper of this series each walking limb of 
Ligia was described as comprising a uniplanar system of alternate flexures. 
This mode of description, adopted for the special purpose then in hand, was 
stated to be incomplete ; for, when the limbs are used not for clinging but 
for progression, a complex movement occurs at the coxo-basal and a more 
simple movement at the mero-carpal articulation, neither of these being in 
the common plane of flexure of the other articulations. As the investiga- 
tion of the first of these movements had involved minute examination of 
the largest male individuals, it was with unusual interest that I learned 
of the existence in the Scottish Oceanographical Laboratory of spirit 
specimens of gigantic isopods whose limb segments could be taken between 
the thumb and forefinger and moved about almost like those of a full- 
grown shore-crab. This isopod is Glyptonotus antarcticus, Eights, one of 
the Idoteidse. 
Dr W. S. Bruce having kindly placed at my disposal a number of the 
laboratory specimens as well as some examples of the related Glyptonotus 
acutus, Richardson, I was able to confirm the result of examination of the 
various articulations in Ligia. Examination of the animals proved to be 
interesting, not only because of the limb flexures but because of other 
structural features. As the existing descriptions of Glyptonotus have 
been written entirely from a systematic point of view, and besides have 
dealt only with the exterior of the animal, I have ventured here to set 
down some additional points relating to its anatomy, many of them sug- 
gested by considerations pertaining to function. It needs no saying that 
function cannot be profitably studied in a dead animal ; at best one can 
only hazard guesses from comparison with the behaviour of allied living 
forms. All functional questions here discussed can be readily settled, 
* The references to preceding papers of this series will he found in the bibliography 
at the end. 
