108
THE BIOLOGY O F EUPHAUSIIDS
some further development the final mature stage illustrated in Fig. 39
is attained. Most male Meganyctiphanes norvegica in the Clyde have
spermatozoa present in the vasa deferentia in December and by the
beginning of February many males have fully formed spermatophores
present in their ejaculatory ducts.
Raab (1915) examined the function of the various regions of the vasa
deferentia in the formation of the spermatophores of M . norvegica and
Mauchline (unpublished) also studied the reproductive organs of this
species. The first part of the was deferens (Fig. 40, a-b) is concerned
solely with the transport of the spermatozoa ; the lumen is bounded by
pavement epithelium whereas the next region (Fig. 40, b-c) has a
thicker cuboidal epithelium which secretes the fluid in which the
spermatozoa are suspended in the spermatophore. This fluid, when the
spermatophore is attached to the female, causes expulsion of the
spermatozoa into the thelycum. The following part of the was deferens
(Fig. 40, c-d), thought by Raab to have no function other than transport of the spermatozoa, is actually responsible for secreting a membrane
or case round the spermatozoa. On approaching the bend (Fig. 40, c)
the lumen of the was deferens becomes elliptical until the region of the
lateral pocket (Fig. 40, lp). The epithelium is now columnar except at
the narrow sides of the lumen where it remains cuboidal. Similar
cuboidal epithelial cells are responsible for secreting the spermatophore
membranes in some decapod Crustacea (Matthews, 1953) and secreted
material was associated with these cells in the vasa deferentia of
M . norvegica examined by Mauchline (unpublished), suggesting that
they may also perform this function in euphausiids. The vas deferens
then turns posteriorly (Fig. 40, d), this part being known as the
spermatophore sac (Fig. 40, sps). Its lumen is pear-shaped t o elliptical
and a layer of circular muscle is present round the now wholly cubical
epithelium. Raab makes no mention of such a layer of muscle in this
region and no muscular layer was found to be associated with any of
the previous parts of the vas deferens. The cement, which attaches the
spermatophore to the thelycum of the female, appears to be secreted
in the lateral pocket. A channel, formed by the walls of the spermatophore sac, leads from the lateral pocket to the proximal region of the
ejaculatory duct where the part of the spermatophore which will be
attached to the female lies. The walls of the spermatophore sac secrete
further material round the mass of spermatozoa and another layer is
secreted in the ejaculatory duct (Fig. 40, ej). The ejaculatory duct
extends from the spermatophore sac ventrally round the body musculature and organs to the paired genital openings and its cuboidal epithelium is bounded by a layer of longitudinal muscle beyond which is a
THE BIOLOGY O F EUPHAUSIIDS
some further development the final mature stage illustrated in Fig. 39
is attained. Most male Meganyctiphanes norvegica in the Clyde have
spermatozoa present in the vasa deferentia in December and by the
beginning of February many males have fully formed spermatophores
present in their ejaculatory ducts.
Raab (1915) examined the function of the various regions of the vasa
deferentia in the formation of the spermatophores of M . norvegica and
Mauchline (unpublished) also studied the reproductive organs of this
species. The first part of the was deferens (Fig. 40, a-b) is concerned
solely with the transport of the spermatozoa ; the lumen is bounded by
pavement epithelium whereas the next region (Fig. 40, b-c) has a
thicker cuboidal epithelium which secretes the fluid in which the
spermatozoa are suspended in the spermatophore. This fluid, when the
spermatophore is attached to the female, causes expulsion of the
spermatozoa into the thelycum. The following part of the was deferens
(Fig. 40, c-d), thought by Raab to have no function other than transport of the spermatozoa, is actually responsible for secreting a membrane
or case round the spermatozoa. On approaching the bend (Fig. 40, c)
the lumen of the was deferens becomes elliptical until the region of the
lateral pocket (Fig. 40, lp). The epithelium is now columnar except at
the narrow sides of the lumen where it remains cuboidal. Similar
cuboidal epithelial cells are responsible for secreting the spermatophore
membranes in some decapod Crustacea (Matthews, 1953) and secreted
material was associated with these cells in the vasa deferentia of
M . norvegica examined by Mauchline (unpublished), suggesting that
they may also perform this function in euphausiids. The vas deferens
then turns posteriorly (Fig. 40, d), this part being known as the
spermatophore sac (Fig. 40, sps). Its lumen is pear-shaped t o elliptical
and a layer of circular muscle is present round the now wholly cubical
epithelium. Raab makes no mention of such a layer of muscle in this
region and no muscular layer was found to be associated with any of
the previous parts of the vas deferens. The cement, which attaches the
spermatophore to the thelycum of the female, appears to be secreted
in the lateral pocket. A channel, formed by the walls of the spermatophore sac, leads from the lateral pocket to the proximal region of the
ejaculatory duct where the part of the spermatophore which will be
attached to the female lies. The walls of the spermatophore sac secrete
further material round the mass of spermatozoa and another layer is
secreted in the ejaculatory duct (Fig. 40, ej). The ejaculatory duct
extends from the spermatophore sac ventrally round the body musculature and organs to the paired genital openings and its cuboidal epithelium is bounded by a layer of longitudinal muscle beyond which is a