250 AMERICAN PARASITIC COPEPODA. 
Of the muscles which move the terminal joint, the flexors are by far 
the most powerful ; whence the ordinary position of these joints. 
The arms in length (1} mm.), transverse wrinkles, &c., resemble 
those of A. percarum, but instead of lying in front of the head have a 
downward direction asin Lerneeopoda. Unlike this genus there is no 
continuously chitinized bulla, and the separation of the plate which 
represents it from the mucous membrane is much more difficult than 
in that form. The plate is somewhat hollowed out on its distal 
surface (cup-shaped in A. percarum V. Nordmann), and from it 
radiate many fine threads of chitin, which undoubtedly are the 
cause of the extremely intimate coalescence with the mucous mem- 
brane. The proximal surface of the plate is strengthened by a 
reticulum of chitinous bars, which become narrower as they approach 
the margin of the plate. 
I have not had the opportunity of examining any living specimens, 
and am thus unable to contribute anything to the further knowledge 
of the soft parts. 
Fig. 5 represents the post-abdomen of the female before the 
spermatophores are attached. The two canals for impregnation open 
upon its extremity: their walls are chitinous, and are especially 
thick posteriorly. In many females the spermatophores (Fig. 3) 
may be found sometimes empty, with the narrow ends of their 
terminal capsules inserted in these orifices, while in others nothing 
remains of the spermatophores, except these capsules. It is in this 
condition that they were interpreted by Claus’ as receptacula seminis 
belonging to the female; but when entire they may usually be 
separated without difficulty from the female post-abdomen; the 
greater or less case with which they may be detached from the 
terminal orifices depending on the amount of cement with which 
they have been attached to the orifices. Occasionally the cement 
may be present in such quantities as to deform the post-abdomen. 
The mode of formation of the brown capsules and of the cement is 
discussed further on. 
The male measures as uch as 1} mm., thus being fully one-third 
of the length of the female. Usually I have found the male attached 
to the post-abdomen of the female, occasionally further forward on 
the body, in one case on the arms. The appendages of the head, 
1 Zeit. wiss. Zool, XI. The similar structures of Lamproglena have been more recently 
(Zeit. wiss. Zool, XXI.) spoken of by Claus as belonging to the spermatophoral apparatus. 
