PRETENDING TO BE A WORM 300 
occupies the tenement, but puts on the guise of the original 
tenant. ‘The whole appearance of the animal is singularly 
like that of a small Serpula, the operculum and. branchiz 
being mimicked by the expanded posterior appendages 
and telson, and the hairs representing the parapodial seta, 
while the smallness of the limbs and the vermiform shape 
of the body, aid in perfecting the resemblance.’ It isya 
sufficiently curious instance of mimicry that the head’ of 
one animal should be imitated by the tail of another. The 
creatures habit of entering the tube head foremost is 
quite in accord with its diminutive antennz and abnor- 
mally small front limbs, and that when not in quest of 
food it should have the branchial appendages of the tail 
near the aperture of ts cave is an obviously convenient 
arrangement. Probably the British Anthura gracilis may 
use a similar shelter, since it is undoubtedly dredged up 
in company with sheils and stones on which the tubes of 
Serpule are abundant. Many of the Edriophthalma 
occupy tubes which they themselves construct. This is 
apparently the case with T'yphlotanais brachyurus, Bed- 
dard, the tube of which is ‘ shaped somewhat like the shell 
of Dentalium.’ The Indian Amphipod, named Concholestes 
dental by Dr. G. M. Giles, forms its tube within a Den- 
talium shell. It seems, however, certainly to belong to the 
genus Cerapus, other species of which have the tubes free. 
Family 2.—Guathiide. 
Though the Gnathiide have been long contented with 
a single genus, the peculiarities of that genus are so great 
that at one time they were supposed to suffice for the 
institution of two separate families. There are striking 
differences that distinguish the sexes from one another and 
the adults from the young. Characters common to all are 
as follows. Both pairs of antenne are short, with the 
flagella clearly marked off from the peduncles; the man- 
dibles are abnormal; the first and last segments of the 
pereeon are very small, and the last perzeopods are want- 
ing; an embryonic character permanenily retained as in 
the genera Hyssura and Cruregens of the preceding family. 
