FAMILY SPHMROMIDA. 97 
to the normal habits of the forms and the quality of bottom 
on which they live. 
In Chapter III it is shown that, speaking broadly, the 
mouth-parts of egg-bearing females are almost always meta- 
morphosed in the genera possessing a well-developed notch, 
while they are generally normal in all other forms. Having 
now shown the use of the notch, it is possible to understand a 
part of that curious connection between the mouth-parts and 
the shape of abdomen in the females with brood. When a 
notch is deep and especially when it turns much upwards the 
nature of the habitat offers hindrances to an easy supply of 
water to the branchiz and from thence to the brood in the 
marsupium or the pouches; in this case the proximal half of 
the maxillipeds is developed as an auxiliary instrument for 
bringing fresh water to the brood, while in the other forms 
the current is produced only by the movements of the pleopods. 
These statements support strongly the assumption set forth 
above (p. 84) that the current produced by the maxillipeds 
runs from behind forwards. One remarkable feature remains, 
viz. that when the proximal half of the maxillipeds is strongly 
expanded all the other parts of the mouth are reduced, but 
this I cannot explain. 
VI. CLASSIFICATION. 
The family Spheeromide is more allied to Cymothoidee (sens. 
lat.), and especially to Serolidz than to any other family of 
Isopoda; in the following characterisation generally only 
those characters are inserted by which it is distinguished 
from the two other families. The diagnoses of the sub-families 
are as complete as possible. The three “Conspectus” of the 
sub-families are analytical only to a certain extent, because it 
has been the intention to give all essential characters for sub- 
divisions of every degree and to avoid unessential particulars. 
Characterisation of the Family Spheromide. 
Head with a well-developed epistome, not divided into frontal 
plate and clypeus, and rarely fused with the upper surface 
vot. 49, PART 1.—NEW SERIES. fi 
