850 PROFESSOR E. RAY LANKESTER, 
branchia, and to distinguish it from the next exite as the 
“lamelliform branchia,” whilst the latter is termed the 
“bottle-shaped branchia.”” But the fact is, that it is 
possible with justice to attribute a respiratory function to 
any such broad lamelliform structure, although it may 
have other important functions. The flabellum is moved 
by three muscular slips arising from the corm, and is first 
of all a swimming or fanning plate. It is more highly 
developed as an “arthrite” than any other of the out- 
growths of the corm. It is somewhat triangular in shape, 
attached by one angle to the corm, and has a setose 
margin. 
The proximal or first exite is not really vesicular although 
frequently described as being so. It is somewhat thicker 
than the flabellum—oval in shape, with a very narrow and 
short pedicle, by which it is connected with the corm. It is 
devoid of seta, and not provided with any muscles. It must 
be regarded as a “ lobe ” (in the sense above defined) rather 
than as an “arthrite.” Throughout the series of limbs where 
present this proximal exite has much the same shape, it is 
always without sete and is invariably devoid of muscular 
connections, although strongly emarginated and attached by 
but a slender neck to the corm. It can therefore have no 
locomotor function, and is, in virtue of negative qualities, the 
branchial outgrowth. On account of its passive character, 
as contrasted with the active fanning flabellum, it may be 
called the dract (bractea—a weather-cock). 
In form the abdominal appendages which follow the first 
post-genital pair agree closely with the latter in all respects, 
except in the reduction of the relative size of the subapical 
lobe. 
In size they undergo a gradual and very great reduction, 
so that the proportionate size of the last of the series is 
represented by the small fig. 13, of Pl. XX. The whole 
appendage is little bigger than the gnathobase of the first 
post-genital limb. 
Gerstaecker’s figure of the thirtieth truncal appendage in 
Apus productus (his Pl. xxx, fig. 10) appears to me to be 
inaccurate. These minute processes are easily mutilated in 
removing them from the body, and such has probably been 
the case with the appendage figured by him. The “ flabel- 
lum” appears to have been broken away in Gerstaecker’s 
specimen, and what he marks as flabellum (d7.) is in reality 
the subapical lobe. 
Abnormal appendage-—Any abnormality ina Crustacean 
appendage is of interest, as showing possible directions of 
