FAMILY SPHAROMIDA. 85 
tioned that in Cerceis and especially in Dynamene (N exsa) 
bidentata (Mont.) I find the differences between mouth-parts 
in adult females (figs. 4.a—4e) and other specimens (figs. 
3 a—3 d) still more astonishing. In both genera more than the 
proximal half of the lower outer surface of the female man- 
dibles is so completely fused with the skeleton of the head 
that even a suture cannot be detected when the mandible 
with the adjoining firm portion of the head is taken out and 
examined under the microscope, while the outer margin itself 
of the mandible protrudes above the skeleton mentioned and 
is indicated on figs. 4a and 4c by dotted lines. Furthermore, 
the distal half of the mandible has not only lost every vestige 
of an incisive dark-coloured part, lacinia and molar process, 
but it shows a very different shape (figs. 4a and 4b as com- 
pared with fig. 3a), being distally rounded, with fine and 
short hairs at the margin. Maxillule and maxille have not 
only lost all sete or spines, but have been much reduced in 
size (figs.4¢ and 4d as compared with figs. 3b and 3c). The 
maxillipeds (fig. 4e¢) have the expansions from epipod and 
from first and second joints much larger than in Cymodoce, 
while the lobe from second joint has been strongly reduced 
in size, the joints of the palp somewhat reduced but yet with 
some short setze on the lobes. 
It is easy without dissection to perceive whether the maxilli- 
peds of an egg-bearing female belonging to this family have 
been altered or have preserved their normal size and shape. 
The question whether the mouth-parts have been meta- 
morphosed can generally be decided without difficulty by 
looking at the end of the mandibles, whether they are very 
dark or yellowish. But an anomaly must be mentioned here. 
Of ten females with marsupium of Cymodoce pilosa 
(M.-Edw.) eight had all their mouth-parts altered as described 
above, but in two specimens the curious feature was observed 
that the maxillipeds and maxille had been completely meta- 
morphosed, while the alterations in the two anterior pairs 
of appendages were less complete. In one of these specimens 
the end of the mandibles had kept their dark colour and the 
