A REMARKABLE CRUSTACEAN PARASITE. Thala 
rently ripe spermatozoa; in another specimen they completely 
filled the dotted area marked ¢e!., obliterating the dorsal and 
posterior region of the perivisceral space. Hach lobe of the 
testis is divided into lobules, and the contents of each lobule 
are all at the same stage of spermatogenetic development. 
The whole organ, as well as each separate lobule, is surrounded 
by a thin, structureless, connective-tissue capsule, and no peri- 
visceral epithelium lines the-capsule externally. A testi- 
cular epithelium of cubic cells with large round nuclei is 
generally visible internally on the proximal side of the organ, 
from which presumably the groups of sperm-cells are derived ; 
it is not visible among or around the lobules themselves. In 
fig. 7 are represented such stages of the spermatogenesis as 
occurred in the sections, arranged as far as possible in develop- 
mental order and forming an incomplete series; in the organ 
itself, however, the position of a lobule in the testis bears no 
relation to the stage of development attained by its contents, 
and the number of sperm-cells included appears also to be 
variable. In stage 1 a number of germinal cells are already 
encapsuled, which in stage 11 have proliferated; the cells then 
appear to enlarge, and the granules of the nucleus, which 
presumably represent the nodes of the nuclear reticulum, stain 
more deeply ; the round nucleus is then replaced by chromatic 
loops (stage Iv), and division appears to take place resulting 
in the formation of cells with small highly-chromatic nuclear 
loops (stage v). At this point there is a wide gap in the series 
which I am unfortunately unable to bridge, stage vi repre- 
senting spermatozoa forming a loose reticulum of thin strands. 
The reticulum becomes closer, the spermatozoa thicken and 
stain very deeply (stage vii), and then arrange themselves with 
their longer axis more or less parallel (stage vir). In the 
vas deferens itself they resemble the last-mentioned stage, and 
lie with their longer axes parallel to each other and to the 
tube. The vasa deferentia on each side pass directly to the end 
of the penis, on which they open separately. 
The ovary (figs. 4, 5) forms a lobate mass on each side of 
the intestine, lying mainly in the carapace in a position 
VOL. XXX, PART 2,—NEW SER. H 
